Methods for controlling temperature in ultrasonic device

ABSTRACT

A generator, ultrasonic device, and method for controlling a temperature of an ultrasonic blade are disclosed. A control circuit coupled to a memory determines an actual resonant frequency of an ultrasonic electromechanical system comprising an ultrasonic transducer coupled to an ultrasonic blade by an ultrasonic waveguide. The actual resonant frequency is correlated to an actual temperature of the ultrasonic blade. The control circuit retrieves from the memory a reference resonant frequency of the ultrasonic electromechanical system. The reference resonant frequency is correlated to a reference temperature of the ultrasonic blade. The control circuit then infers the temperature of the ultrasonic blade based on the difference between the actual resonant frequency and the reference resonant frequency. The control circuit controls the temperature of the ultrasonic blade based on the inferred temperature

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. § 119(e)to U.S. Provisional Patent Application Ser. No. 62/640,417, titledTEMPERATURE CONTROL IN ULTRASONIC DEVICE AND CONTROL SYSTEM THEREFOR,filed Mar. 8, 2018, and to U.S. Provisional Patent Application Ser. No.62/640,415, titled ESTIMATING STATE OF ULTRASONIC END EFFECTOR ANDCONTROL SYSTEM THEREFOR, filed Mar. 8, 2018, the disclosure of each ofwhich is herein incorporated by reference in its entirety.

BACKGROUND

In a surgical environment, smart energy devices may be needed in a smartenergy architecture environment. Ultrasonic surgical devices, such asultrasonic scalpels, are finding increasingly widespread applications insurgical procedures by virtue of their unique performancecharacteristics. Depending upon specific device configurations andoperational parameters, ultrasonic surgical devices can providesubstantially simultaneous transection of tissue and homeostasis bycoagulation, desirably minimizing patient trauma. An ultrasonic surgicaldevice may comprise a handpiece containing an ultrasonic transducer, andan instrument coupled to the ultrasonic transducer having adistally-mounted end effector (e.g., a blade tip) to cut and sealtissue. In some cases, the instrument may be permanently affixed to thehandpiece. In other cases, the instrument may be detachable from thehandpiece, as in the case of a disposable instrument or aninterchangeable instrument. The end effector transmits ultrasonic energyto tissue brought into contact with the end effector to realize cuttingand sealing action. Ultrasonic surgical devices of this nature can beconfigured for open surgical use, laparoscopic, or endoscopic surgicalprocedures including robotic-assisted procedures.

Ultrasonic energy cuts and coagulates tissue using temperatures lowerthan those used in electrosurgical procedures and can be transmitted tothe end effector by an ultrasonic generator in communication with thehandpiece. Vibrating at high frequencies (e.g., 55,500 cycles persecond), the ultrasonic blade denatures protein in the tissue to form asticky coagulum. Pressure exerted on tissue by the blade surfacecollapses blood vessels and allows the coagulum to form a hemostaticseal. A surgeon can control the cutting speed and coagulation by theforce applied to the tissue by the end effector, the time over which theforce is applied, and the selected excursion level of the end effector.

The ultrasonic transducer may be modeled as an equivalent circuitcomprising a first branch having a static capacitance and a second“motional” branch having a serially connected inductance, resistance andcapacitance that define the electromechanical properties of a resonator.Known ultrasonic generators may include a tuning inductor for tuning outthe static capacitance at a resonant frequency so that substantially allof a generator's drive signal current flows into the motional branch.Accordingly, by using a tuning inductor, the generator's drive signalcurrent represents the motional branch current, and the generator isthus able to control its drive signal to maintain the ultrasonictransducer's resonant frequency. The tuning inductor may also transformthe phase impedance plot of the ultrasonic transducer to improve thegenerator's frequency lock capabilities. However, the tuning inductormust be matched with the specific static capacitance of an ultrasonictransducer at the operational resonant frequency. In other words, adifferent ultrasonic transducer having a different static capacitancerequires a different tuning inductor.

Additionally, in some ultrasonic generator architectures, thegenerator's drive signal exhibits asymmetrical harmonic distortion thatcomplicates impedance magnitude and phase measurements. For example, theaccuracy of impedance phase measurements may be reduced due to harmonicdistortion in the current and voltage signals.

Moreover, electromagnetic interference in noisy environments decreasesthe ability of the generator to maintain lock on the ultrasonictransducer's resonant frequency, increasing the likelihood of invalidcontrol algorithm inputs.

Electrosurgical devices for applying electrical energy to tissue inorder to treat and/or destroy the tissue are also finding increasinglywidespread applications in surgical procedures. An electrosurgicaldevice may comprise a handpiece and an instrument having adistally-mounted end effector (e.g., one or more electrodes). The endeffector can be positioned against the tissue such that electricalcurrent is introduced into the tissue. Electrosurgical devices can beconfigured for bipolar or monopolar operation. During bipolar operation,current is introduced into and returned from the tissue by active andreturn electrodes, respectively, of the end effector. During monopolaroperation, current is introduced into the tissue by an active electrodeof the end effector and returned through a return electrode (e.g., agrounding pad) separately located on a patient's body. Heat generated bythe current flowing through the tissue may form hemostatic seals withinthe tissue and/or between tissues and thus may be particularly usefulfor sealing blood vessels, for example. The end effector of anelectrosurgical device may also comprise a cutting member that ismovable relative to the tissue and the electrodes to transect thetissue.

Electrical energy applied by an electrosurgical device can betransmitted to the instrument by a generator in communication with thehandpiece. The electrical energy may be in the form of radio frequency(RF) energy. RF energy is a form of electrical energy that may be in thefrequency range of 300 kHz to 1 MHz, as described inEN60601-2-2:2009+A11:2011, Definition 201.3.218—HIGH FREQUENCY. Forexample, the frequencies in monopolar RF applications are typicallyrestricted to less than 5 MHz. However, in bipolar RF applications, thefrequency can be almost any value. Frequencies above 200 kHz aretypically used for monopolar applications in order to avoid the unwantedstimulation of nerves and muscles which would result from the use of lowfrequency current. Lower frequencies may be used for bipolar techniquesif a risk analysis shows the possibility of neuromuscular stimulationhas been mitigated to an acceptable level. Normally, frequencies above 5MHz are not used in order to minimize the problems associated with highfrequency leakage currents. It is generally recognized that 10 mA is thelower threshold of thermal effects on tissue.

During its operation, an electrosurgical device can transmit lowfrequency RF energy through tissue, which causes ionic agitation, orfriction, in effect resistive heating, thereby increasing thetemperature of the tissue. Because a sharp boundary may be createdbetween the affected tissue and the surrounding tissue, surgeons canoperate with a high level of precision and control, without sacrificingun-targeted adjacent tissue. The low operating temperatures of RF energymay be useful for removing, shrinking, or sculpting soft tissue whilesimultaneously sealing blood vessels. RF energy may work particularlywell on connective tissue, which is primarily comprised of collagen andshrinks when contacted by heat.

Due to their unique drive signal, sensing and feedback needs, ultrasonicand electrosurgical devices have generally required differentgenerators. Additionally, in cases where the instrument is disposable orinterchangeable with a handpiece, ultrasonic and electrosurgicalgenerators are limited in their ability to recognize the particularinstrument configuration being used and to optimize control anddiagnostic processes accordingly. Moreover, capacitive coupling betweenthe non-isolated and patient-isolated circuits of the generator,especially in cases where higher voltages and frequencies are used, mayresult in exposure of a patient to unacceptable levels of leakagecurrent.

Furthermore, due to their unique drive signal, sensing and feedbackneeds, ultrasonic and electrosurgical devices have generally requireddifferent user interfaces for the different generators. In suchconventional ultrasonic and electrosurgical devices, one user interfaceis configured for use with an ultrasonic instrument whereas a differentuser interface may be configured for use with an electrosurgicalinstrument. Such user interfaces include hand and/or foot activated userinterfaces such as hand activated switches and/or foot activatedswitches. As various aspects of combined generators for use with bothultrasonic and electrosurgical instruments are contemplated in thesubsequent disclosure, additional user interfaces that are configured tooperate with both ultrasonic and/or electrosurgical instrumentgenerators also are contemplated.

Additional user interfaces for providing feedback, whether to the useror other machine, are contemplated within the subsequent disclosure toprovide feedback indicating an operating mode or status of either anultrasonic and/or electrosurgical instrument. Providing user and/ormachine feedback for operating a combination ultrasonic and/orelectrosurgical instrument will require providing sensory feedback to auser and electrical/mechanical/electro-mechanical feedback to a machine.Feedback devices that incorporate visual feedback devices (e.g., an LCDdisplay screen, LED indicators), audio feedback devices (e.g., aspeaker, a buzzer) or tactile feedback devices (e.g., haptic actuators)for use in combined ultrasonic and/or electrosurgical instruments arecontemplated in the subsequent disclosure.

Other electrical surgical instruments include, without limitation,irreversible and/or reversible electroporation, and/or microwavetechnologies, among others. Accordingly, the techniques disclosed hereinare applicable to ultrasonic, bipolar or monopolar RF (electrosurgical),irreversible and/or reversible electroporation, and/or microwave basedsurgical instruments, among others.

SUMMARY

In one general aspect, a method is provided. The method is configuredfor controlling a temperature of an ultrasonic blade, the methodcomprising: determining, by a control circuit coupled to a memory, anactual resonant frequency of an ultrasonic electromechanical systemcomprising an ultrasonic transducer coupled to an ultrasonic blade by anultrasonic waveguide, wherein the actual resonant frequency iscorrelated to an actual temperature of the ultrasonic blade; retrieving,from the memory by the control circuit, a reference resonant frequencyof the ultrasonic electromechanical system, wherein the referenceresonant frequency is correlated to a reference temperature of theultrasonic blade; inferring, by the control circuit, the temperature ofthe ultrasonic blade based on the difference between the actual resonantfrequency and the reference resonant frequency; and controlling, by thecontrol circuit, the temperature of the ultrasonic blade based on theinferred temperature.

In another aspect, a generator is provided. The generator is configuredfor controlling a temperature of an ultrasonic blade, the generatorcomprising: a control circuit coupled to a memory, the control circuitconfigured to: determine an actual resonant frequency of an ultrasonicelectromechanical system comprising an ultrasonic transducer coupled toan ultrasonic blade by an ultrasonic waveguide, wherein the actualresonant frequency is correlated to an actual temperature of theultrasonic blade; retrieve from the memory a reference resonantfrequency of the ultrasonic electromechanical system, wherein thereference resonant frequency is correlated to a reference temperature ofthe ultrasonic blade; infer the temperature of the ultrasonic bladebased on the difference between the actual resonant frequency and thereference resonant frequency; and control the temperature of theultrasonic blade based on the inferred temperature.

In yet another aspect, an ultrasonic device is provided. The ultrasonicdevice is configured for controlling a temperature of an ultrasonicblade, the ultrasonic device comprising: a control circuit coupled to amemory, the control circuit configured to: determine an actual resonantfrequency of an ultrasonic electromechanical system comprising anultrasonic transducer coupled to an ultrasonic blade by an ultrasonicwaveguide, wherein the actual resonant frequency is correlated to anactual temperature of the ultrasonic blade; retrieve from the memory areference resonant frequency of the ultrasonic electromechanical system,wherein the reference resonant frequency is correlated to a referencetemperature of the ultrasonic blade; infer the temperature of theultrasonic blade based on the difference between the actual resonantfrequency and the reference resonant frequency; and control thetemperature of the ultrasonic blade based on the inferred temperature.

FIGURES

The features of various aspects are set forth with particularity in theappended claims. The various aspects, however, both as to organizationand methods of operation, together with further objects and advantagesthereof, may best be understood by reference to the followingdescription, taken in conjunction with the accompanying drawings asfollows.

FIG. 1 is a system configured to execute adaptive ultrasonic bladecontrol algorithms in a surgical data network comprising a modularcommunication hub, in accordance with at least one aspect of the presentdisclosure.

FIG. 2 illustrates an example of a generator, in accordance with atleast one aspect of the present disclosure.

FIG. 3 is a surgical system comprising a generator and various surgicalinstruments usable therewith, in accordance with at least one aspect ofthe present disclosure.

FIG. 4 is an end effector, in accordance with at least one aspect of thepresent disclosure.

FIG. 5 is a diagram of the surgical system of FIG. 3, in accordance withat least one aspect of the present disclosure.

FIG. 6 is a model illustrating motional branch current, in accordancewith at least one aspect of the present disclosure.

FIG. 7 is a structural view of a generator architecture, in accordancewith at least one aspect of the present disclosure.

FIGS. 8A-8C are functional views of a generator architecture, inaccordance with at least one aspect of the present disclosure.

FIGS. 9A-9B are structural and functional aspects of a generator, inaccordance with at least one aspect of the present disclosure.

FIG. 10 illustrates a control circuit configured to control aspects ofthe surgical instrument or tool, in accordance with at least one aspectof the present disclosure.

FIG. 11 illustrates a combinational logic circuit configured to controlaspects of the surgical instrument or tool, in accordance with at leastone aspect of the present disclosure.

FIG. 12 illustrates a sequential logic circuit configured to controlaspects of the surgical instrument or tool, in accordance with at leastone aspect of the present disclosure.

FIG. 13 illustrates one aspect of a fundamental architecture for adigital synthesis circuit such as a direct digital synthesis (DDS)circuit configured to generate a plurality of wave shapes for theelectrical signal waveform for use in a surgical instrument, inaccordance with at least one aspect of the present disclosure.

FIG. 14 illustrates one aspect of direct digital synthesis (DDS) circuitconfigured to generate a plurality of wave shapes for the electricalsignal waveform for use in surgical instrument, in accordance with atleast one aspect of the present disclosure.

FIG. 15 illustrates one cycle of a discrete time digital electricalsignal waveform, in accordance with at least one aspect of the presentdisclosure of an analog waveform (shown superimposed over a discretetime digital electrical signal waveform for comparison purposes), inaccordance with at least one aspect of the present disclosure.

FIG. 16 is a diagram of a control system configured to provideprogressive closure of a closure member as it advances distally to closethe clamp arm to apply a closure force load at a desired rate accordingto one aspect of this disclosure.

FIG. 17 illustrates a proportional-integral-derivative (PID) controllerfeedback control system according to one aspect of this disclosure.

FIG. 18 is an alternative system for controlling the frequency of anultrasonic electromechanical system and detecting the impedance thereof,in accordance with at least one aspect of the present disclosure.

FIGS. 19A-19B are complex impedance spectra of the same ultrasonicdevice with a cold (solid line) and hot (broken line) ultrasonic blade,in accordance with at least one aspect of the present disclosure, where

FIG. 19A is a graphical representation of impedance phase angle as afunction of resonant frequency of the same ultrasonic device with a cold(solid line) and hot (broken line) ultrasonic blade; and

FIG. 19B is a graphical representation of impedance magnitude as afunction of resonant frequency of the same ultrasonic device with a cold(solid line) and hot (broken line) ultrasonic blade.

FIG. 20 is a diagram of a Kalman filter to improve temperature estimatorand state space model based on impedance across an ultrasonic transducermeasured at a variety of frequencies, in accordance with at least oneaspect of the present disclosure.

FIG. 21 are three probability distributions employed by a stateestimator of the Kalman filter shown in FIG. 20 to maximize estimates,in accordance with at least one aspect of the present disclosure.

FIG. 22A is a graphical representation of temperature versus time of anultrasonic device with no temperature control reaching a maximumtemperature of 490° C.

FIG. 22B is a graphical representation of temperature versus time of anultrasonic device with temperature control reaching a maximumtemperature of 320° C., in accordance with at least one aspect of thepresent disclosure.

FIG. 23 is a graphical representation of the relationship betweeninitial frequency and the change in frequency required to achieve atemperature of approximately 340° C., in accordance with at least oneaspect of the present disclosure.

FIG. 24 illustrates a feedback control system comprising an ultrasonicgenerator to regulate the electrical current (i) set point applied to anultrasonic transducer of an ultrasonic electromechanical system toprevent the frequency (f) of the ultrasonic transducer from decreasinglower than a predetermined threshold, in accordance with at least oneaspect of the present disclosure.

FIG. 25 is a logic flow diagram of a process depicting a control programor a logic configuration of a controlled thermal management process toprotect an end effector pad, in accordance with at least one aspect ofthe present disclosure.

FIG. 26 is a graphical representation of temperature versus timecomparing the desired temperature of an ultrasonic blade with a smartultrasonic blade and a conventional ultrasonic blade, in accordance withat least one aspect of the present disclosure.

FIGS. 27A-27B are graphical representations of feedback control toadjust ultrasonic power applied to an ultrasonic transducer when asudden drop in temperature of an ultrasonic blade is detected, where

FIG. 27A is a graphical representation of ultrasonic power as a functionof time; and

FIG. 27B is a plot of ultrasonic blade temperature as a function oftime, in accordance with at least one aspect of the present disclosure.

FIG. 28 is a logic flow diagram of a process depicting a control programor a logic configuration to control the temperature of an ultrasonicblade, in accordance with at least one aspect of the present disclosure.

FIG. 29 is a graphical representation of ultrasonic blade temperature asa function of time during a vessel firing, in accordance with at leastone aspect of the present disclosure.

FIG. 30 is a logic flow diagram of a process depicting a control programor a logic configuration to control the temperature of an ultrasonicblade between two temperature set points, in accordance with at leastone aspect of the present disclosure.

FIG. 31 is a logic flow diagram of a process depicting a control programor a logic configuration to determine the initial temperature of anultrasonic blade, in accordance with at least one aspect of the presentdisclosure.

FIG. 32 is a logic flow diagram of a process depicting a control programor a logic configuration to determine when an ultrasonic blade isapproaching instability and then adjusting the power to the ultrasonictransducer to prevent instability of the ultrasonic transducer, inaccordance with at least one aspect of the present disclosure.

FIG. 33 is a logic flow diagram of a process depicting a control programor a logic configuration to provide ultrasonic sealing with temperaturecontrol, in accordance with at least one aspect of the presentdisclosure.

FIG. 34 are graphical representations of ultrasonic transducer currentand ultrasonic blade temperature as a function of time, in accordancewith at least one aspect of the present disclosure.

DESCRIPTION

Applicant of the present patent application also owns the followingcontemporaneously-filed U.S. patent applications, each of which isherein incorporated by reference in its entirety:

-   -   U.S. patent application Ser. No. 16/144,345, titled ULTRASONIC        SEALING ALGORITHM WITH TEMPERATURE CONTROL, now U.S. Patent        Application Publication No. 2019/0274718;    -   U.S. patent application Ser. No. 16/144,351, titled APPLICATION        OF SMART ULTRASONIC BLADE TECHNOLOGY, now U.S. Patent        Application Publication No. 2019/0274705;    -   U.S. patent application Ser. No. 16/144,423, titled ADAPTIVE        ADVANCED TISSUE TREATMENT PAD SAVER MODE, now U.S. Patent        Application Publication No. 2019/0274709;    -   U.S. patent application Ser. No. 16/144,455, titled SMART BLADE        TECHNOLOGY TO CONTROL BLADE INSTABILITY, now U.S. Patent        Application Publication No. 2019/0274712; and    -   U.S. patent application Ser. No. 16/144,483, titled START        TEMPERATURE OF BLADE, now U.S. Patent Application Publication        No. 2019/0274720.

Applicant of the present patent application also owns the followingcontemporaneously-filed U.S. patent applications, each of which isherein incorporated by reference in its entirety:

-   -   U.S. patent application Ser. No. 16/144,383, titled METHODS FOR        ESTIMATING AND CONTROLLING STATE OF ULTRASONIC END EFFECTOR, now        U.S. Patent Application Publication No. 2019/0274706;    -   U.S. patent application Ser. No. 16/144,391, titled IN-THE-JAW        CLASSIFIER BASED ON MODEL, now U.S. Patent Application        Publication No. 2019/0274719;    -   U.S. patent application Ser. No. 16/144,397, titled APPLICATION        OF SMART BLADE TECHNOLOGY, now U.S. Patent Application        Publication No. 2019/0274707;    -   U.S. patent application Ser. No. 16/144,405, titled SMART BLADE        AND POWER PULSING, now U.S. Patent Application Publication No.        2019/0274708;    -   U.S. patent application Ser. No. 16/144,418, titled ADJUSTMENT        OF COMPLEX IMPEDANCE TO COMPENSATE FOR LOST POWER IN AN        ARTICULATING ULTRASONIC DEVICE, now U.S. Patent Application        Publication No. 2019/0274662;    -   U.S. patent application Ser. No. 16/144,427, titled USING        SPECTROSCOPY TO DETERMINE DEVICE USE STATE IN COMBO INSTRUMENT,        now U.S. Patent Application Publication No. 2019/0274710;    -   U.S. patent application Ser. No. 16/144,434, titled VESSEL        SENSING FOR ADAPTIVE ADVANCED HEMOSTASIS, now U.S. Patent        Application Publication No. 2019/0274711;    -   U.S. patent application Ser. No. 16/144,460, titled CALCIFIED        VESSEL IDENTIFICATION, now U.S. Patent Application Publication        No. 2019/0274713;    -   U.S. patent application Ser. No. 16/144,472, titled DETECTION OF        LARGE VESSELS DURING PARENCHYMAL DISSECTION USING A SMART BLADE,        now U.S. Patent Application Publication No. 2019/0274749;    -   U.S. patent application Ser. No. 16/144,478, titled SMART BLADE        APPLICATION FOR REUSABLE AND DISPOSABLE DEVICES, now U.S. Patent        Application Publication No. 2019/0274714;    -   U.S. patent application Ser. No. 16/144,486, titled LIVE TIME        TISSUE CLASSIFICATION USING ELECTRICAL PARAMETERS, now U.S.        Patent Application Publication No. 2019/0274750; and    -   U.S. patent application Ser. No. 16/144,508, titled FINE        DISSECTION MODE FOR TISSUE CLASSIFICATION, now U.S. Patent        Application Publication No. 2019/0274752.

Applicant of the present application owns the following U.S. PatentApplications, filed on Sep. 10, 2018, the disclosure of each of which isherein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application Ser. No. 62/729,177, titled        AUTOMATED DATA SCALING, ALIGNMENT, AND ORGANIZING BASED ON        PREDEFINED PARAMETERS WITHIN A SURGICAL NETWORK BEFORE        TRANSMISSION;    -   U.S. provisional Patent Application Ser. No. 62/729,182, titled        SENSING THE PATIENT POSITION AND CONTACT UTILIZING THE        MONO-POLAR RETURN PAD ELECTRODE TO PROVIDE SITUATIONAL AWARENESS        TO THE HUB;    -   U.S. Provisional Patent Application Ser. No. 62/729,184, titled        POWERED SURGICAL TOOL WITH A PREDEFINED ADJUSTABLE CONTROL        ALGORITHM FOR CONTROLLING AT LEAST ONE END-EFFECTOR PARAMETER        AND A MEANS FOR LIMITING THE ADJUSTMENT;    -   U.S. Provisional Patent Application Ser. No. 62/729,183, titled        SURGICAL NETWORK RECOMMENDATIONS FROM REAL TIME ANALYSIS OF        PROCEDURE VARIABLES AGAINST A BASELINE HIGHLIGHTING DIFFERENCES        FROM THE OPTIMAL SOLUTION;    -   U.S. Provisional Patent Application Ser. No. 62/729,191, titled        A CONTROL FOR A SURGICAL NETWORK OR SURGICAL NETWORK CONNECTED        DEVICE THAT ADJUSTS ITS FUNCTION BASED ON A SENSED SITUATION OR        USAGE;    -   U.S. Provisional Patent Application Ser. No. 62/729,176, titled        INDIRECT COMMAND AND CONTROL OF A FIRST OPERATING ROOM SYSTEM        THROUGH THE USE OF A SECOND OPERATING ROOM SYSTEM WITHIN A        STERILE FIELD WHERE THE SECOND OPERATING ROOM SYSTEM HAS PRIMARY        AND SECONDARY OPERATING MODES;    -   U.S. Provisional Patent Application Ser. No. 62/729,186, titled        WIRELESS PAIRING OF A SURGICAL DEVICE WITH ANOTHER DEVICE WITHIN        A STERILE SURGICAL FIELD BASED ON THE USAGE AND SITUATIONAL        AWARENESS OF DEVICES; and    -   U.S. Provisional Patent Application Ser. No. 62/729,185, titled        POWERED STAPLING DEVICE THAT IS CAPABLE OF ADJUSTING FORCE,        ADVANCEMENT SPEED, AND OVERALL STROKE OF CUTTING MEMBER OF THE        DEVICE BASED ON SENSED PARAMETER OF FIRING OR CLAMPING.

Applicant of the present application owns the following U.S. PatentApplications, filed on Aug. 28, 2018, the disclosure of each of which isherein incorporated by reference in its entirety:

-   -   U.S. patent application Ser. No. 16/115,214, titled ESTIMATING        STATE OF ULTRASONIC END EFFECTOR AND CONTROL SYSTEM THEREFOR;    -   U.S. patent application Ser. No. 16/115,205, titled TEMPERATURE        CONTROL OF ULTRASONIC END EFFECTOR AND CONTROL SYSTEM THEREFOR;    -   U.S. patent application Ser. No. 16/115,233, titled RADIO        FREQUENCY ENERGY DEVICE FOR DELIVERING COMBINED ELECTRICAL        SIGNALS;    -   U.S. patent application Ser. No. 16/115,208, titled CONTROLLING        AN ULTRASONIC SURGICAL INSTRUMENT ACCORDING TO TISSUE LOCATION;    -   U.S. patent application Ser. No. 16/115,220, titled CONTROLLING        ACTIVATION OF AN ULTRASONIC SURGICAL INSTRUMENT ACCORDING TO THE        PRESENCE OF TISSUE;    -   U.S. patent application Ser. No. 16/115,232, titled DETERMINING        TISSUE COMPOSITION VIA AN ULTRASONIC SYSTEM;    -   U.S. patent application Ser. No. 16/115,239, titled DETERMINING        THE STATE OF AN ULTRASONIC ELECTROMECHANICAL SYSTEM ACCORDING TO        FREQUENCY SHIFT;    -   U.S. patent application Ser. No. 16/115,247, titled DETERMINING        THE STATE OF AN ULTRASONIC END EFFECTOR;    -   U.S. patent application Ser. No. 16/115,211, titled SITUATIONAL        AWARENESS OF ELECTROSURGICAL SYSTEMS;    -   U.S. patent application Ser. No. 16/115,226, titled MECHANISMS        FOR CONTROLLING DIFFERENT ELECTROMECHANICAL SYSTEMS OF AN        ELECTROSURGICAL INSTRUMENT;    -   U.S. patent application Ser. No. 16/115,240, titled DETECTION OF        END EFFECTOR EMERSION IN LIQUID;    -   U.S. patent application Ser. No. 16/115,249, titled INTERRUPTION        OF ENERGY DUE TO INADVERTENT CAPACITIVE COUPLING;    -   U.S. patent application Ser. No. 16/115,256, titled INCREASING        RADIO FREQUENCY TO CREATE PAD-LESS MONOPOLAR LOOP;    -   U.S. patent application Ser. No. 16/115,223, titled BIPOLAR        COMBINATION DEVICE THAT AUTOMATICALLY ADJUSTS PRESSURE BASED ON        ENERGY MODALITY; and    -   U.S. patent application Ser. No. 16/115,238, titled ACTIVATION        OF ENERGY DEVICES.

Applicant of the present application owns the following U.S. PatentApplications, filed on Aug. 23, 2018, the disclosure of each of which isherein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application No. 62/721,995, titled        CONTROLLING AN ULTRASONIC SURGICAL INSTRUMENT ACCORDING TO        TISSUE LOCATION;    -   U.S. Provisional Patent Application No. 62/721,998, titled        SITUATIONAL AWARENESS OF ELECTROSURGICAL SYSTEMS;    -   U.S. Provisional Patent Application No. 62/721,999, titled        INTERRUPTION OF ENERGY DUE TO INADVERTENT CAPACITIVE COUPLING;    -   U.S. Provisional Patent Application No. 62/721,994, titled        BIPOLAR COMBINATION DEVICE THAT AUTOMATICALLY ADJUSTS PRESSURE        BASED ON ENERGY MODALITY; and    -   U.S. Provisional Patent Application No. 62/721,996, titled RADIO        FREQUENCY ENERGY DEVICE FOR DELIVERING COMBINED ELECTRICAL        SIGNALS.

Applicant of the present application owns the following U.S. PatentApplications, filed on Jun. 30, 2018, the disclosure of each of which isherein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application No. 62/692,747, titled SMART        ACTIVATION OF AN ENERGY DEVICE BY ANOTHER DEVICE;    -   U.S. Provisional Patent Application No. 62/692,748, titled SMART        ENERGY ARCHITECTURE; and    -   U.S. Provisional Patent Application No. 62/692,768, titled SMART        ENERGY DEVICES. Applicant of the present application owns the        following U.S. Patent Applications, filed on Jun. 29, 2018, the        disclosure of each of which is herein incorporated by reference        in its entirety:    -   U.S. patent application Ser. No. 16/024,090, titled CAPACITIVE        COUPLED RETURN PATH PAD WITH SEPARABLE ARRAY ELEMENTS;    -   U.S. patent application Ser. No. 16/024,057, titled CONTROLLING        A SURGICAL INSTRUMENT ACCORDING TO SENSED CLOSURE PARAMETERS;    -   U.S. patent application Ser. No. 16/024,067, titled SYSTEMS FOR        ADJUSTING END EFFECTOR PARAMETERS BASED ON PERIOPERATIVE        INFORMATION;    -   U.S. patent application Ser. No. 16/024,075, titled SAFETY        SYSTEMS FOR SMART POWERED SURGICAL STAPLING;    -   U.S. patent application Ser. No. 16/024,083, titled SAFETY        SYSTEMS FOR SMART POWERED SURGICAL STAPLING;    -   U.S. patent application Ser. No. 16/024,094, titled SURGICAL        SYSTEMS FOR DETECTING END EFFECTOR TISSUE DISTRIBUTION        IRREGULARITIES;    -   U.S. patent application Ser. No. 16/024,138, titled SYSTEMS FOR        DETECTING PROXIMITY OF SURGICAL END EFFECTOR TO CANCEROUS        TISSUE;    -   U.S. patent application Ser. No. 16/024,150, titled SURGICAL        INSTRUMENT CARTRIDGE SENSOR ASSEMBLIES;    -   U.S. patent application Ser. No. 16/024,160, titled VARIABLE        OUTPUT CARTRIDGE SENSOR ASSEMBLY;    -   U.S. patent application Ser. No. 16/024,124, titled SURGICAL        INSTRUMENT HAVING A FLEXIBLE ELECTRODE;    -   U.S. patent application Ser. No. 16/024,132, titled SURGICAL        INSTRUMENT HAVING A FLEXIBLE CIRCUIT;    -   U.S. patent application Ser. No. 16/024,141, titled SURGICAL        INSTRUMENT WITH A TISSUE MARKING ASSEMBLY;    -   U.S. patent application Ser. No. 16/024,162, titled SURGICAL        SYSTEMS WITH PRIORITIZED DATA TRANSMISSION CAPABILITIES;    -   U.S. patent application Ser. No. 16/024,066, titled SURGICAL        EVACUATION SENSING AND MOTOR CONTROL;    -   U.S. patent application Ser. No. 16/024,096, titled SURGICAL        EVACUATION SENSOR ARRANGEMENTS;    -   U.S. patent application Ser. No. 16/024,116, titled SURGICAL        EVACUATION FLOW PATHS;    -   U.S. patent application Ser. No. 16/024,149, titled SURGICAL        EVACUATION SENSING AND GENERATOR CONTROL;    -   U.S. patent application Ser. No. 16/024,180, titled SURGICAL        EVACUATION SENSING AND DISPLAY;    -   U.S. patent application Ser. No. 16/024,245, titled        COMMUNICATION OF SMOKE EVACUATION SYSTEM PARAMETERS TO HUB OR        CLOUD IN SMOKE EVACUATION MODULE FOR INTERACTIVE SURGICAL        PLATFORM;    -   U.S. patent application Ser. No. 16/024,258, titled SMOKE        EVACUATION SYSTEM INCLUDING A SEGMENTED CONTROL CIRCUIT FOR        INTERACTIVE SURGICAL PLATFORM;    -   U.S. patent application Ser. No. 16/024,265, titled SURGICAL        EVACUATION SYSTEM WITH A COMMUNICATION CIRCUIT FOR COMMUNICATION        BETWEEN A FILTER AND A SMOKE EVACUATION DEVICE; and    -   U.S. patent application Ser. No. 16/024,273, titled DUAL        IN-SERIES LARGE AND SMALL DROPLET FILTERS.

Applicant of the present application owns the following U.S. ProvisionalPatent Applications, filed on Jun. 28, 2018, the disclosure of each ofwhich is herein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application Ser. No. 62/691,228, titled        A METHOD OF USING REINFORCED FLEX CIRCUITS WITH MULTIPLE SENSORS        WITH ELECTROSURGICAL DEVICES;    -   U.S. Provisional Patent Application Ser. No. 62/691,227, titled        CONTROLLING A SURGICAL INSTRUMENT ACCORDING TO SENSED CLOSURE        PARAMETERS;    -   U.S. Provisional Patent Application Ser. No. 62/691,230, titled        SURGICAL INSTRUMENT HAVING A FLEXIBLE ELECTRODE;    -   U.S. Provisional Patent Application Ser. No. 62/691,219, titled        SURGICAL EVACUATION SENSING AND MOTOR CONTROL;    -   U.S. Provisional Patent Application Ser. No. 62/691,257, titled        COMMUNICATION OF SMOKE EVACUATION SYSTEM PARAMETERS TO HUB OR        CLOUD IN SMOKE EVACUATION MODULE FOR INTERACTIVE SURGICAL        PLATFORM;    -   U.S. Provisional Patent Application Ser. No. 62/691,262, titled        SURGICAL EVACUATION SYSTEM WITH A COMMUNICATION CIRCUIT FOR        COMMUNICATION BETWEEN A FILTER AND A SMOKE EVACUATION DEVICE;        and    -   U.S. Provisional Patent Application Ser. No. 62/691,251, titled        DUAL IN-SERIES LARGE AND SMALL DROPLET FILTERS.

Applicant of the present application owns the following U.S. ProvisionalPatent Application, filed on Apr. 19, 2018, the disclosure of each ofwhich is herein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application Ser. No. 62/659,900, titled        METHOD OF HUB COMMUNICATION.

Applicant of the present application owns the following U.S. ProvisionalPatent Applications, filed on Mar. 30, 2018, the disclosure of each ofwhich is herein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application No. 62/650,898 filed on Mar.        30, 2018, titled CAPACITIVE COUPLED RETURN PATH PAD WITH        SEPARABLE ARRAY ELEMENTS;    -   U.S. Provisional Patent Application Ser. No. 62/650,887, titled        SURGICAL SYSTEMS WITH OPTIMIZED SENSING CAPABILITIES;    -   U.S. Provisional Patent Application Ser. No. 62/650,882, titled        SMOKE EVACUATION MODULE FOR INTERACTIVE SURGICAL PLATFORM; and    -   U.S. Provisional Patent Application Ser. No. 62/650,877, titled        SURGICAL SMOKE EVACUATION SENSING AND CONTROLS

Applicant of the present application owns the following U.S. PatentApplications, filed on Mar. 29, 2018, the disclosure of each of which isherein incorporated by reference in its entirety:

-   -   U.S. patent application Ser. No. 15/940,641, titled INTERACTIVE        SURGICAL SYSTEMS WITH ENCRYPTED COMMUNICATION CAPABILITIES;    -   U.S. patent application Ser. No. 15/940,648, titled INTERACTIVE        SURGICAL SYSTEMS WITH CONDITION HANDLING OF DEVICES AND DATA        CAPABILITIES;    -   U.S. patent application Ser. No. 15/940,656, titled SURGICAL HUB        COORDINATION OF CONTROL AND COMMUNICATION OF OPERATING ROOM        DEVICES;    -   U.S. patent application Ser. No. 15/940,666, titled SPATIAL        AWARENESS OF SURGICAL HUBS IN OPERATING ROOMS;    -   U.S. patent application Ser. No. 15/940,670, titled COOPERATIVE        UTILIZATION OF DATA DERIVED FROM SECONDARY SOURCES BY        INTELLIGENT SURGICAL HUBS;    -   U.S. patent application Ser. No. 15/940,677, titled SURGICAL HUB        CONTROL ARRANGEMENTS;    -   U.S. patent application Ser. No. 15/940,632, titled DATA        STRIPPING METHOD TO INTERROGATE PATIENT RECORDS AND CREATE        ANONYMIZED RECORD;    -   U.S. patent application Ser. No. 15/940,640, titled        COMMUNICATION HUB AND STORAGE DEVICE FOR STORING PARAMETERS AND        STATUS OF A SURGICAL DEVICE TO BE SHARED WITH CLOUD BASED        ANALYTICS SYSTEMS;    -   U.S. patent application Ser. No. 15/940,645, titled SELF        DESCRIBING DATA PACKETS GENERATED AT AN ISSUING INSTRUMENT;    -   U.S. patent application Ser. No. 15/940,649, titled DATA PAIRING        TO INTERCONNECT A DEVICE MEASURED PARAMETER WITH AN OUTCOME;    -   U.S. patent application Ser. No. 15/940,654, titled SURGICAL HUB        SITUATIONAL AWARENESS;    -   U.S. patent application Ser. No. 15/940,663, titled SURGICAL        SYSTEM DISTRIBUTED PROCESSING;    -   U.S. patent application Ser. No. 15/940,668, titled AGGREGATION        AND REPORTING OF SURGICAL HUB DATA;    -   U.S. patent application Ser. No. 15/940,671, titled SURGICAL HUB        SPATIAL AWARENESS TO DETERMINE DEVICES IN OPERATING THEATER;    -   U.S. patent application Ser. No. 15/940,686, titled DISPLAY OF        ALIGNMENT OF STAPLE CARTRIDGE TO PRIOR LINEAR STAPLE LINE;    -   U.S. patent application Ser. No. 15/940,700, titled STERILE        FIELD INTERACTIVE CONTROL DISPLAYS;    -   U.S. patent application Ser. No. 15/940,629, titled COMPUTER        IMPLEMENTED INTERACTIVE SURGICAL SYSTEMS;    -   U.S. patent application Ser. No. 15/940,704, titled USE OF LASER        LIGHT AND RED-GREEN-BLUE COLORATION TO DETERMINE PROPERTIES OF        BACK SCATTERED LIGHT;    -   U.S. patent application Ser. No. 15/940,722, titled        CHARACTERIZATION OF TISSUE IRREGULARITIES THROUGH THE USE OF        MONO-CHROMATIC LIGHT REFRACTIVITY; and    -   U.S. patent application Ser. No. 15/940,742, titled DUAL CMOS        ARRAY IMAGING.    -   U.S. patent application Ser. No. 15/940,636, titled ADAPTIVE        CONTROL PROGRAM UPDATES FOR SURGICAL DEVICES;    -   U.S. patent application Ser. No. 15/940,653, titled ADAPTIVE        CONTROL PROGRAM UPDATES FOR SURGICAL HUBS;    -   U.S. patent application Ser. No. 15/940,660, titled CLOUD-BASED        MEDICAL ANALYTICS FOR CUSTOMIZATION AND RECOMMENDATIONS TO A        USER;    -   U.S. patent application Ser. No. 15/940,679, titled CLOUD-BASED        MEDICAL ANALYTICS FOR LINKING OF LOCAL USAGE TRENDS WITH THE        RESOURCE ACQUISITION BEHAVIORS OF LARGER DATA SET;    -   U.S. patent application Ser. No. 15/940,694, titled CLOUD-BASED        MEDICAL ANALYTICS FOR MEDICAL FACILITY SEGMENTED        INDIVIDUALIZATION OF INSTRUMENT FUNCTION;    -   U.S. patent application Ser. No. 15/940,634, titled CLOUD-BASED        MEDICAL ANALYTICS FOR SECURITY AND AUTHENTICATION TRENDS AND        REACTIVE MEASURES;    -   U.S. patent application Ser. No. 15/940,706, titled DATA        HANDLING AND PRIORITIZATION IN A CLOUD ANALYTICS NETWORK; and    -   U.S. patent application Ser. No. 15/940,675, titled CLOUD        INTERFACE FOR COUPLED SURGICAL DEVICES.    -   U.S. patent application Ser. No. 15/940,627, titled DRIVE        ARRANGEMENTS FOR ROBOT-ASSISTED SURGICAL PLATFORMS;    -   U.S. patent application Ser. No. 15/940,637, titled        COMMUNICATION ARRANGEMENTS FOR ROBOT-ASSISTED SURGICAL        PLATFORMS;    -   U.S. patent application Ser. No. 15/940,642, titled CONTROLS FOR        ROBOT-ASSISTED SURGICAL PLATFORMS;    -   U.S. patent application Ser. No. 15/940,676, titled AUTOMATIC        TOOL ADJUSTMENTS FOR ROBOT-ASSISTED SURGICAL PLATFORMS;    -   U.S. patent application Ser. No. 15/940,680, titled CONTROLLERS        FOR ROBOT-ASSISTED SURGICAL PLATFORMS;    -   U.S. patent application Ser. No. 15/940,683, titled COOPERATIVE        SURGICAL ACTIONS FOR ROBOT-ASSISTED SURGICAL PLATFORMS;    -   U.S. patent application Ser. No. 15/940,690, titled DISPLAY        ARRANGEMENTS FOR ROBOT-ASSISTED SURGICAL PLATFORMS; and    -   U.S. patent application Ser. No. 15/940,711, titled SENSING        ARRANGEMENTS FOR ROBOT-ASSISTED SURGICAL PLATFORMS.

Applicant of the present application owns the following U.S. ProvisionalPatent Applications, filed on Mar. 28, 2018, the disclosure of each ofwhich is herein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application Ser. No. 62/649,302, titled        INTERACTIVE SURGICAL SYSTEMS WITH ENCRYPTED COMMUNICATION        CAPABILITIES;    -   U.S. Provisional Patent Application Ser. No. 62/649,294, titled        DATA STRIPPING METHOD TO INTERROGATE PATIENT RECORDS AND CREATE        ANONYMIZED RECORD;    -   U.S. Provisional Patent Application Ser. No. 62/649,300, titled        SURGICAL HUB SITUATIONAL AWARENESS;    -   U.S. Provisional Patent Application Ser. No. 62/649,309, titled        SURGICAL HUB SPATIAL AWARENESS TO DETERMINE DEVICES IN OPERATING        THEATER;    -   U.S. Provisional Patent Application Ser. No. 62/649,310, titled        COMPUTER IMPLEMENTED INTERACTIVE SURGICAL SYSTEMS;    -   U.S. Provisional Patent Application Ser. No. 62/649,291, titled        USE OF LASER LIGHT AND RED-GREEN-BLUE COLORATION TO DETERMINE        PROPERTIES OF BACK SCATTERED LIGHT;    -   U.S. Provisional Patent Application Ser. No. 62/649,296, titled        ADAPTIVE CONTROL PROGRAM UPDATES FOR SURGICAL DEVICES;    -   U.S. Provisional Patent Application Ser. No. 62/649,333, titled        CLOUD-BASED MEDICAL ANALYTICS FOR CUSTOMIZATION AND        RECOMMENDATIONS TO A USER;    -   U.S. Provisional Patent Application Ser. No. 62/649,327, titled        CLOUD-BASED MEDICAL ANALYTICS FOR SECURITY AND AUTHENTICATION        TRENDS AND REACTIVE MEASURES;    -   U.S. Provisional Patent Application Ser. No. 62/649,315, titled        DATA HANDLING AND PRIORITIZATION IN A CLOUD ANALYTICS NETWORK;    -   U.S. Provisional Patent Application Ser. No. 62/649,313, titled        CLOUD INTERFACE FOR COUPLED SURGICAL DEVICES;    -   U.S. Provisional Patent Application Ser. No. 62/649,320, titled        DRIVE ARRANGEMENTS FOR ROBOT-ASSISTED SURGICAL PLATFORMS;    -   U.S. Provisional Patent Application Ser. No. 62/649,307, titled        AUTOMATIC TOOL ADJUSTMENTS FOR ROBOT-ASSISTED SURGICAL        PLATFORMS; and    -   U.S. Provisional Patent Application Ser. No. 62/649,323, titled        SENSING ARRANGEMENTS FOR ROBOT-ASSISTED SURGICAL PLATFORMS.

Applicant of the present application owns the following U.S. ProvisionalPatent Applications, filed on Dec. 28, 2017, the disclosure of each ofwhich is herein incorporated by reference in its entirety:

-   -   U.S. Provisional Patent Application Serial No. U.S. Provisional        Patent Application Ser. No. 62/611,341, titled INTERACTIVE        SURGICAL PLATFORM;    -   U.S. Provisional Patent Application Ser. No. 62/611,340, titled        CLOUD-BASED MEDICAL ANALYTICS; and    -   U.S. Provisional Patent Application Ser. No. 62/611,339, titled        ROBOT ASSISTED SURGICAL PLATFORM.

Before explaining various aspects of surgical devices and generators indetail, it should be noted that the illustrative examples are notlimited in application or use to the details of construction andarrangement of parts illustrated in the accompanying drawings anddescription. The illustrative examples may be implemented orincorporated in other aspects, variations and modifications, and may bepracticed or carried out in various ways. Further, unless otherwiseindicated, the terms and expressions employed herein have been chosenfor the purpose of describing the illustrative examples for theconvenience of the reader and are not for the purpose of limitationthereof. Also, it will be appreciated that one or more of thefollowing-described aspects, expressions of aspects, and/or examples,can be combined with any one or more of the other following-describedaspects, expressions of aspects and/or examples.

Various aspects are directed to improved ultrasonic surgical devices,electrosurgical devices and generators for use therewith. Aspects of theultrasonic surgical devices can be configured for transecting and/orcoagulating tissue during surgical procedures, for example. Aspects ofthe electrosurgical devices can be configured for transecting,coagulating, scaling, welding and/or desiccating tissue during surgicalprocedures, for example.

Adaptive Ultrasonic Blade Control Algorithms

In various aspects smart ultrasonic energy devices may comprise adaptivealgorithms to control the operation of the ultrasonic blade. In oneaspect, the ultrasonic blade adaptive control algorithms are configuredto identify tissue type and adjust device parameters. In one aspect, theultrasonic blade control algorithms are configured to parameterizetissue type. An algorithm to detect the collagen/elastic ratio of tissueto tune the amplitude of the distal tip of the ultrasonic blade isdescribed in the following section of the present disclosure. Variousaspects of smart ultrasonic energy devices are described herein inconnection with FIGS. 1-34, for example. Accordingly, the followingdescription of adaptive ultrasonic blade control algorithms should beread in conjunction with FIGS. 1-34 and the description associatedtherewith.

Tissue Type Identification and Device Parameter Adjustments

In certain surgical procedures it would be desirable to employ adaptiveultrasonic blade control algorithms. In one aspect, adaptive ultrasonicblade control algorithms may be employed to adjust the parameters of theultrasonic device based on the type of tissue in contact with theultrasonic blade. In one aspect, the parameters of the ultrasonic devicemay be adjusted based on the location of the tissue within the jaws ofthe ultrasonic end effector, for example, the location of the tissuebetween the clamp arm and the ultrasonic blade. The impedance of theultrasonic transducer may be employed to differentiate what percentageof the tissue is located in the distal or proximal end of the endeffector. The reactions of the ultrasonic device may be based on thetissue type or compressibility of the tissue. In another aspect, theparameters of the ultrasonic device may be adjusted based on theidentified tissue type or parameterization. For example, the mechanicaldisplacement amplitude of the distal tip of the ultrasonic blade may betuned based on the ration of collagen to elastin tissue detected duringthe tissue identification procedure. The ratio of collagen to elastintissue may be detected used a variety of techniques including infrared(IR) surface reflectance and emissivity. The force applied to the tissueby the clamp arm and/or the stroke of the clamp arm to produce gap andcompression. Electrical continuity across a jaw equipped with electrodesmay be employed to determine what percentage of the jaw is covered withtissue.

FIG. 1 is a system 800 configured to execute adaptive ultrasonic bladecontrol algorithms in a surgical data network comprising a modularcommunication hub, in accordance with at least one aspect of the presentdisclosure. In one aspect, the generator module 240 is configured toexecute the adaptive ultrasonic blade control algorithm(s) 802 asdescribed herein with reference to FIGS. 25-34. In another aspect, thedevice/instrument 235 is configured to execute the adaptive ultrasonicblade control algorithm(s) 804 as described herein with reference toFIGS. 25-34. In another aspect, both the device/instrument 235 and thedevice/instrument 235 are configured to execute the adaptive ultrasonicblade control algorithms 802, 804 as described herein with reference toFIGS. 25-34.

The generator module 240 may comprise a patient isolated stage incommunication with a non-isolated stage via a power transformer. Asecondary winding of the power transformer is contained in the isolatedstage and may comprise a tapped configuration (e.g., a center-tapped ora non-center-tapped configuration) to define drive signal outputs fordelivering drive signals to different surgical instruments, such as, forexample, an ultrasonic surgical instrument, an RF electrosurgicalinstrument, and a multifunction surgical instrument which includesultrasonic and RF energy modes that can be delivered alone orsimultaneously. In particular, the drive signal outputs may output anultrasonic drive signal (e.g., a 420V root-mean-square (RMS) drivesignal) to an ultrasonic surgical instrument 241, and the drive signaloutputs may output an RF electrosurgical drive signal (e.g., a 100V RMSdrive signal) to an RF electrosurgical instrument 241. Aspects of thegenerator module 240 are described herein with reference to FIGS. 1-9B.

The generator module 240 or the device/instrument 235 or both arecoupled to the modular control tower 236 connected to multiple operatingtheater devices such as, for example, intelligent surgical instruments,robots, and other computerized devices located in the operating theater.In some aspects, a surgical data network may include a modularcommunication hub configured to connect modular devices located in oneor more operating theaters of a healthcare facility, or any room in ahealthcare facility specially equipped for surgical operations, to acloud-based system (e.g., the cloud 204 that may include a remote server213 coupled to a storage device).

Modular devices located in the operating theater may be coupled to themodular communication hub. The network hub and/or the network switch maybe coupled to a network router to connect the devices to the cloud 204or a local computer system. Data associated with the devices may betransferred to cloud-based computers via the router for remote dataprocessing and manipulation. Data associated with the devices may alsobe transferred to a local computer system for local data processing andmanipulation. Modular devices located in the same operating theater alsomay be coupled to a network switch. The network switch may be coupled tothe network hub and/or the network router to connect to the devices tothe cloud 204. Data associated with the devices may be transferred tothe cloud 204 via the network router for data processing andmanipulation. Data associated with the devices may also be transferredto the local computer system for local data processing and manipulation.

It will be appreciated that cloud computing relies on sharing computingresources rather than having local servers or personal devices to handlesoftware applications. The word “cloud” may be used as a metaphor for“the Internet,” although the term is not limited as such. Accordingly,the term “cloud computing” may be used herein to refer to “a type ofInternet-based computing,” where different services—such as servers,storage, and applications—are delivered to the modular communication huband/or computer system located in the surgical theater (e.g., a fixed,mobile, temporary, or field operating room or space) and to devicesconnected to the modular communication hub and/or computer systemthrough the Internet. The cloud infrastructure may be maintained by acloud service provider. In this context, the cloud service provider maybe the entity that coordinates the usage and control of the deviceslocated in one or more operating theaters. The cloud computing servicescan perform a large number of calculations based on the data gathered bysmart surgical instruments, robots, and other computerized deviceslocated in the operating theater. The hub hardware enables multipledevices or connections to be connected to a computer that communicateswith the cloud computing resources and storage.

FIG. 1 further illustrates some aspects of a computer-implementedinteractive surgical system comprising a modular communication hub thatmay include the system 800 configured to execute adaptive ultrasonicblade control algorithms in a surgical data network. The surgical systemmay include at least one surgical hub in communication with a cloud 204that may include a remote server 213. In one aspect, thecomputer-implemented interactive surgical system comprises a modularcontrol tower 236 connected to multiple operating theater devices suchas, for example, intelligent surgical instruments, robots, and othercomputerized devices located in the operating theater. The modularcontrol tower 236 may comprise a modular communication hub coupled to acomputer system. In some aspects, the modular control tower 236 iscoupled to an imaging module that is coupled to an endoscope, agenerator module 240 that is coupled to an energy device 241, and asmart device/instrument 235 optionally coupled to a display 237. Theoperating theater devices are coupled to cloud computing resources anddata storage via the modular control tower 236. A robot hub 222 also maybe connected to the modular control tower 236 and to the cloud computingresources. The devices/instruments 235, visualization systems 208, amongothers, may be coupled to the modular control tower 236 via wired orwireless communication standards or protocols, as described herein. Themodular control tower 236 may be coupled to a hub display 215 (e.g.,monitor, screen) to display and overlay images received from the imagingmodule, device/instrument display, and/or other visualization systems208. The hub display 215 also may display data received from devicesconnected to the modular control tower in conjunction with images andoverlaid images.

Generator Hardware

FIG. 2 illustrates an example of a generator 900, which is one form of agenerator configured to couple to an ultrasonic instrument and furtherconfigured to execute adaptive ultrasonic blade control algorithms in asurgical data network comprising a modular communication hub as shown inFIG. 1. The generator 900 is configured to deliver multiple energymodalities to a surgical instrument. The generator 900 provides RF andultrasonic signals for delivering energy to a surgical instrument eitherindependently or simultaneously. The RF and ultrasonic signals may beprovided alone or in combination and may be provided simultaneously. Asnoted above, at least one generator output can deliver multiple energymodalities (e.g., ultrasonic, bipolar or monopolar RF, irreversibleand/or reversible electroporation, and/or microwave energy, amongothers) through a single port, and these signals can be deliveredseparately or simultaneously to the end effector to treat tissue. Thegenerator 900 comprises a processor 902 coupled to a waveform generator904. The processor 902 and waveform generator 904 are configured togenerate a variety of signal waveforms based on information stored in amemory coupled to the processor 902, not shown for clarity ofdisclosure. The digital information associated with a waveform isprovided to the waveform generator 904 which includes one or more DACcircuits to convert the digital input into an analog output. The analogoutput is fed to an amplifier 1106 for signal conditioning andamplification. The conditioned and amplified output of the amplifier 906is coupled to a power transformer 908. The signals are coupled acrossthe power transformer 908 to the secondary side, which is in the patientisolation side. A first signal of a first energy modality is provided tothe surgical instrument between the terminals labeled ENERGY₁ andRETURN. A second signal of a second energy modality is coupled across acapacitor 910 and is provided to the surgical instrument between theterminals labeled ENERGY₂ and RETURN. It will be appreciated that morethan two energy modalities may be output and thus the subscript “n” maybe used to designate that up to n ENERGY_(n) terminals may be provided,where n is a positive integer greater than 1. It also will beappreciated that up to “n” return paths RETURN_(n) may be providedwithout departing from the scope of the present disclosure.

A first voltage sensing circuit 912 is coupled across the terminalslabeled ENERGY₁ and the RETURN path to measure the output voltagetherebetween. A second voltage sensing circuit 924 is coupled across theterminals labeled ENERGY₂ and the RETURN path to measure the outputvoltage therebetween. A current sensing circuit 914 is disposed inseries with the RETURN leg of the secondary side of the powertransformer 908 as shown to measure the output current for either energymodality. If different return paths are provided for each energymodality, then a separate current sensing circuit should be provided ineach return leg. The outputs of the first and second voltage sensingcircuits 912, 924 are provided to respective isolation transformers 916,922 and the output of the current sensing circuit 914 is provided toanother isolation transformer 918. The outputs of the isolationtransformers 916, 928, 922 in the on the primary side of the powertransformer 908 (non-patient isolated side) are provided to a one ormore ADC circuit 926. The digitized output of the ADC circuit 926 isprovided to the processor 902 for further processing and computation.The output voltages and output current feedback information can beemployed to adjust the output voltage and current provided to thesurgical instrument and to compute output impedance, among otherparameters. Input/output communications between the processor 902 andpatient isolated circuits is provided through an interface circuit 920.Sensors also may be in electrical communication with the processor 902by way of the interface circuit 920.

In one aspect, the impedance may be determined by the processor 902 bydividing the output of either the first voltage sensing circuit 912coupled across the terminals labeled ENERGY₁/RETURN or the secondvoltage sensing circuit 924 coupled across the terminals labeledENERGY₂/RETURN by the output of the current sensing circuit 914 disposedin series with the RETURN leg of the secondary side of the powertransformer 908. The outputs of the first and second voltage sensingcircuits 912, 924 are provided to separate isolations transformers 916,922 and the output of the current sensing circuit 914 is provided toanother isolation transformer 916. The digitized voltage and currentsensing measurements from the ADC circuit 926 are provided the processor902 for computing impedance. As an example, the first energy modalityENERGY₁ may be ultrasonic energy and the second energy modality ENERGY₂may be RF energy. Nevertheless, in addition to ultrasonic and bipolar ormonopolar RF energy modalities, other energy modalities includeirreversible and/or reversible electroporation and/or microwave energy,among others. Also, although the example illustrated in FIG. 2 shows asingle return path RETURN may be provided for two or more energymodalities, in other aspects, multiple return paths RETURN_(n) may beprovided for each energy modality ENERGY_(n). Thus, as described herein,the ultrasonic transducer impedance may be measured by dividing theoutput of the first voltage sensing circuit 912 by the current sensingcircuit 914 and the tissue impedance may be measured by dividing theoutput of the second voltage sensing circuit 924 by the current sensingcircuit 914.

As shown in FIG. 2, the generator 900 comprising at least one outputport can include a power transformer 908 with a single output and withmultiple taps to provide power in the form of one or more energymodalities, such as ultrasonic, bipolar or monopolar RF, irreversibleand/or reversible electroporation, and/or microwave energy, amongothers, for example, to the end effector depending on the type oftreatment of tissue being performed. For example, the generator 900 candeliver energy with higher voltage and lower current to drive anultrasonic transducer, with lower voltage and higher current to drive RFelectrodes for sealing tissue, or with a coagulation waveform for spotcoagulation using either monopolar or bipolar RF electrosurgicalelectrodes. The output waveform from the generator 900 can be steered,switched, or filtered to provide the frequency to the end effector ofthe surgical instrument. The connection of an ultrasonic transducer tothe generator 900 output would be preferably located between the outputlabeled ENERGY₁ and RETURN as shown in FIG. 2. In one example, aconnection of RF bipolar electrodes to the generator 900 output would bepreferably located between the output labeled ENERGY₂ and RETURN. In thecase of monopolar output, the preferred connections would be activeelectrode (e.g., pencil or other probe) to the ENERGY₂ output and asuitable return pad connected to the RETURN output.

Additional details are disclosed in U.S. Patent Application PublicationNo. 2017/0086914, titled TECHNIQUES FOR OPERATING GENERATOR FORDIGITALLY GENERATING ELECTRICAL SIGNAL WAVEFORMS AND SURGICALINSTRUMENTS, which published on Mar. 30, 2017, which is hereinincorporated by reference in its entirety.

As used throughout this description, the term “wireless” and itsderivatives may be used to describe circuits, devices, systems, methods,techniques, communications channels, etc., that may communicate datathrough the use of modulated electromagnetic radiation through anon-solid medium. The term does not imply that the associated devices donot contain any wires, although in some aspects they might not. Thecommunication module may implement any of a number of wireless or wiredcommunication standards or protocols, including but not limited to Wi-Fi(IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE 802.20, long termevolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE, GSM, GPRS, CDMA,TDMA, DECT, Bluetooth, Ethernet derivatives thereof, as well as anyother wireless and wired protocols that are designated as 3G, 4G, 5G,and beyond. The computing module may include a plurality ofcommunication modules. For instance, a first communication module may bededicated to shorter range wireless communications such as Wi-Fi andBluetooth and a second communication module may be dedicated to longerrange wireless communications such as GPS, EDGE, GPRS, CDMA, WiMAX, LTE,Ev-DO, and others.

As used herein a processor or processing unit is an electronic circuitwhich performs operations on some external data source, usually memoryor some other data stream. The term is used herein to refer to thecentral processor (central processing unit) in a system or computersystems (especially systems on a chip (SoCs)) that combine a number ofspecialized “processors.”

As used herein, a system on a chip or system on chip (SoC or SOC) is anintegrated circuit (also known as an “IC” or “chip”) that integrates allcomponents of a computer or other electronic systems. It may containdigital, analog, mixed-signal, and often radio-frequency functions—allon a single substrate. A SoC integrates a microcontroller (ormicroprocessor) with advanced peripherals like graphics processing unit(GPU), Wi-Fi module, or coprocessor. A SoC may or may not containbuilt-in memory.

As used herein, a microcontroller or controller is a system thatintegrates a microprocessor with peripheral circuits and memory. Amicrocontroller (or MCU for microcontroller unit) may be implemented asa small computer on a single integrated circuit. It may be similar to aSoC; an SoC may include a microcontroller as one of its components. Amicrocontroller may contain one or more core processing units (CPUs)along with memory and programmable input/output peripherals. Programmemory in the form of Ferroelectric RAM, NOR flash or OTP ROM is alsooften included on chip, as well as a small amount of RAM.Microcontrollers may be employed for embedded applications, in contrastto the microprocessors used in personal computers or other generalpurpose applications consisting of various discrete chips.

As used herein, the term controller or microcontroller may be astand-alone IC or chip device that interfaces with a peripheral device.This may be a link between two parts of a computer or a controller on anexternal device that manages the operation of (and connection with) thatdevice.

Any of the processors or microcontrollers described herein, may beimplemented by any single core or multicore processor such as thoseknown under the trade name ARM Cortex by Texas Instruments. In oneaspect, the processor may be an LM4F230H5QR ARM Cortex-M4F ProcessorCore, available from Texas Instruments, for example, comprising on-chipmemory of 256 KB single-cycle flash memory, or other non-volatilememory, up to 40 MHz, a prefetch buffer to improve performance above 40MHz, a 32 KB single-cycle serial random access memory (SRAM), internalread-only memory (ROM) loaded with StellarisWare® software, 2 KBelectrically erasable programmable read-only memory (EEPROM), one ormore pulse width modulation (PWM) modules, one or more quadratureencoder inputs (QEI) analog, one or more 12-bit Analog-to-DigitalConverters (ADC) with 12 analog input channels, details of which areavailable for the product datasheet.

In one aspect, the processor may comprise a safety controller comprisingtwo controller-based families such as TMS570 and RM4x known under thetrade name Hercules ARM Cortex R4, also by Texas Instruments. The safetycontroller may be configured specifically for IEC 61508 and ISO 26262safety critical applications, among others, to provide advancedintegrated safety features while delivering scalable performance,connectivity, and memory options.

Modular devices include the modules (as described in connection withFIG. 3, for example) that are receivable within a surgical hub and thesurgical devices or instruments that can be connected to the variousmodules in order to connect or pair with the corresponding surgical hub.The modular devices include, for example, intelligent surgicalinstruments, medical imaging devices, suction/irrigation devices, smokeevacuators, energy generators, ventilators, insufflators, and displays.The modular devices described herein can be controlled by controlalgorithms. The control algorithms can be executed on the modular deviceitself, on the surgical hub to which the particular modular device ispaired, or on both the modular device and the surgical hub (e.g., via adistributed computing architecture). In some exemplifications, themodular devices' control algorithms control the devices based on datasensed by the modular device itself (i.e., by sensors in, on, orconnected to the modular device). This data can be related to thepatient being operated on (e.g., tissue properties or insufflationpressure) or the modular device itself (e.g., the rate at which a knifeis being advanced, motor current, or energy levels). For example, acontrol algorithm for a surgical stapling and cutting instrument cancontrol the rate at which the instrument's motor drives its knifethrough tissue according to resistance encountered by the knife as itadvances.

FIG. 3 illustrates one form of a surgical system 1000 comprising agenerator 1100 and various surgical instruments 1104, 1106, 1108 usabletherewith, where the surgical instrument 1104 is an ultrasonic surgicalinstrument, the surgical instrument 1106 is an RF electrosurgicalinstrument, and the multifunction surgical instrument 1108 is acombination ultrasonic/RF electrosurgical instrument. The generator 1100is configurable for use with a variety of surgical instruments.According to various forms, the generator 1100 may be configurable foruse with different surgical instruments of different types including,for example, ultrasonic surgical instruments 1104, RF electrosurgicalinstruments 1106, and multifunction surgical instruments 1108 thatintegrate RF and ultrasonic energies delivered simultaneously from thegenerator 1100. Although in the form of FIG. 3 the generator 1100 isshown separate from the surgical instruments 1104, 1106, 1108 in oneform, the generator 1100 may be formed integrally with any of thesurgical instruments 1104, 1106, 1108 to form a unitary surgical system.The generator 1100 comprises an input device 1110 located on a frontpanel of the generator 1100 console. The input device 1110 may compriseany suitable device that generates signals suitable for programming theoperation of the generator 1100. The generator 1100 may be configuredfor wired or wireless communication.

The generator 1100 is configured to drive multiple surgical instruments1104, 1106, 1108. The first surgical instrument is an ultrasonicsurgical instrument 1104 and comprises a handpiece 1105 (HP), anultrasonic transducer 1120, a shaft 1126, and an end effector 1122. Theend effector 1122 comprises an ultrasonic blade 1128 acousticallycoupled to the ultrasonic transducer 1120 and a clamp arm 1140. Thehandpiece 1105 comprises a trigger 1143 to operate the clamp arm 1140and a combination of the toggle buttons 1134 a, 1134 b, 1134 c toenergize and drive the ultrasonic blade 1128 or other function. Thetoggle buttons 1134 a, 1134 b, 1134 c can be configured to energize theultrasonic transducer 1120 with the generator 1100.

The generator 1100 also is configured to drive a second surgicalinstrument 1106. The second surgical instrument 1106 is an RFelectrosurgical instrument and comprises a handpiece 1107 (HP), a shaft1127, and an end effector 1124. The end effector 1124 compriseselectrodes in clamp arms 1142 a, 1142 b and return through an electricalconductor portion of the shaft 1127. The electrodes are coupled to andenergized by a bipolar energy source within the generator 1100. Thehandpiece 1107 comprises a trigger 1145 to operate the clamp arms 1142a, 1142 b and an energy button 1135 to actuate an energy switch toenergize the electrodes in the end effector 1124.

The generator 1100 also is configured to drive a multifunction surgicalinstrument 1108. The multifunction surgical instrument 1108 comprises ahandpiece 1109 (HP), a shaft 1129, and an end effector 1125. The endeffector 1125 comprises an ultrasonic blade 1149 and a clamp arm 1146.The ultrasonic blade 1149 is acoustically coupled to the ultrasonictransducer 1120. The handpiece 1109 comprises a trigger 1147 to operatethe clamp arm 1146 and a combination of the toggle buttons 1137 a, 1137b, 1137 c to energize and drive the ultrasonic blade 1149 or otherfunction. The toggle buttons 1137 a, 1137 b, 1137 c can be configured toenergize the ultrasonic transducer 1120 with the generator 1100 andenergize the ultrasonic blade 1149 with a bipolar energy source alsocontained within the generator 1100.

The generator 1100 is configurable for use with a variety of surgicalinstruments. According to various forms, the generator 1100 may beconfigurable for use with different surgical instruments of differenttypes including, for example, the ultrasonic surgical instrument 1104,the RF electrosurgical instrument 1106, and the multifunction surgicalinstrument 1108 that integrates RF and ultrasonic energies deliveredsimultaneously from the generator 1100. Although in the form of FIG. 3the generator 1100 is shown separate from the surgical instruments 1104,1106, 1108, in another form the generator 1100 may be formed integrallywith any one of the surgical instruments 1104, 1106, 1108 to form aunitary surgical system. As discussed above, the generator 1100comprises an input device 1110 located on a front panel of the generator1100 console. The input device 1110 may comprise any suitable devicethat generates signals suitable for programming the operation of thegenerator 1100. The generator 1100 also may comprise one or more outputdevices 1112. Further aspects of generators for digitally generatingelectrical signal waveforms and surgical instruments are described in USpatent publication US-2017-0086914-A1, which is herein incorporated byreference in its entirety.

FIG. 4 is an end effector 1122 of the example ultrasonic device 1104, inaccordance with at least one aspect of the present disclosure. The endeffector 1122 may comprise a blade 1128 that may be coupled to theultrasonic transducer 1120 via a wave guide. When driven by theultrasonic transducer 1120, the blade 1128 may vibrate and, when broughtinto contact with tissue, may cut and/or coagulate the tissue, asdescribed herein. According to various aspects, and as illustrated inFIG. 4, the end effector 1122 may also comprise a clamp arm 1140 thatmay be configured for cooperative action with the blade 1128 of the endeffector 1122. With the blade 1128, the clamp arm 1140 may comprise aset of jaws. The clamp arm 1140 may be pivotally connected at a distalend of a shaft 1126 of the instrument portion 1104. The clamp arm 1140may include a clamp arm tissue pad 1163, which may be formed fromTEFLON® or other suitable low-friction material. The pad 1163 may bemounted for cooperation with the blade 1128, with pivotal movement ofthe clamp arm 1140 positioning the clamp pad 1163 in substantiallyparallel relationship to, and in contact with, the blade 1128. By thisconstruction, a tissue bite to be clamped may be grasped between thetissue pad 1163 and the blade 1128. The tissue pad 1163 may be providedwith a sawtooth-like configuration including a plurality of axiallyspaced, proximally extending gripping teeth 1161 to enhance the grippingof tissue in cooperation with the blade 1128. The clamp arm 1140 maytransition from the open position shown in FIG. 4 to a closed position(with the clamp arm 1140 in contact with or proximity to the blade 1128)in any suitable manner. For example, the handpiece 1105 may comprise ajaw closure trigger. When actuated by a clinician, the jaw closuretrigger may pivot the clamp arm 1140 in any suitable manner.

The generator 1100 may be activated to provide the drive signal to theultrasonic transducer 1120 in any suitable manner. For example, thegenerator 1100 may comprise a foot switch 1430 (FIG. 5) coupled to thegenerator 1100 via a footswitch cable 1432. A clinician may activate theultrasonic transducer 1120, and thereby the ultrasonic transducer 1120and blade 1128, by depressing the foot switch 1430. In addition, orinstead of the foot switch 1430, some aspects of the device 1104 mayutilize one or more switches positioned on the handpiece 1105 that, whenactivated, may cause the generator 1100 to activate the ultrasonictransducer 1120. In one aspect, for example, the one or more switchesmay comprise a pair of toggle buttons 1134 a, 1134 b, 1134 c (FIG. 3),for example, to determine an operating mode of the device 1104. When thetoggle button 1134 a is depressed, for example, the ultrasonic generator1100 may provide a maximum drive signal to the ultrasonic transducer1120, causing it to produce maximum ultrasonic energy output. Depressingtoggle button 1134 b may cause the ultrasonic generator 1100 to providea user-selectable drive signal to the ultrasonic transducer 1120,causing it to produce less than the maximum ultrasonic energy output.The device 1104 additionally or alternatively may comprise a secondswitch to, for example, indicate a position of a jaw closure trigger foroperating the jaws via the clamp arm 1140 of the end effector 1122.Also, in some aspects, the ultrasonic generator 1100 may be activatedbased on the position of the jaw closure trigger, (e.g., as theclinician depresses the jaw closure trigger to close the jaws via theclamp arm 1140, ultrasonic energy may be applied).

Additionally or alternatively, the one or more switches may comprise atoggle button 1134 c that, when depressed, causes the generator 1100 toprovide a pulsed output (FIG. 3). The pulses may be provided at anysuitable frequency and grouping, for example. In certain aspects, thepower level of the pulses may be the power levels associated with togglebuttons 1134 a, 1134 b (maximum, less than maximum), for example.

It will be appreciated that a device 1104 may comprise any combinationof the toggle buttons 1134 a, 1134 b, 1134 c (FIG. 3). For example, thedevice 1104 could be configured to have only two toggle buttons: atoggle button 1134 a for producing maximum ultrasonic energy output anda toggle button 1134 c for producing a pulsed output at either themaximum or less than maximum power level per. In this way, the drivesignal output configuration of the generator 1100 could be fivecontinuous signals, or any discrete number of individual pulsed signals(1, 2, 3, 4, or 5). In certain aspects, the specific drive signalconfiguration may be controlled based upon, for example, EEPROM settingsin the generator 1100 and/or user power level selection(s).

In certain aspects, a two-position switch may be provided as analternative to a toggle button 1134 c (FIG. 3). For example, a device1104 may include a toggle button 1134 a for producing a continuousoutput at a maximum power level and a two-position toggle button 1134 b.In a first detented position, toggle button 1134 b may produce acontinuous output at a less than maximum power level, and in a seconddetented position the toggle button 1134 b may produce a pulsed output(e.g., at either a maximum or less than maximum power level, dependingupon the EEPROM settings).

In some aspects, the RF electrosurgical end effector 1124, 1125 (FIG. 3)may also comprise a pair of electrodes. The electrodes may be incommunication with the generator 1100, for example, via a cable. Theelectrodes may be used, for example, to measure an impedance of a tissuebite present between the clamp arm 1142 a, 1146 and the blade 1142 b,1149. The generator 1100 may provide a signal (e.g., a non-therapeuticsignal) to the electrodes. The impedance of the tissue bite may befound, for example, by monitoring the current, voltage, etc. of thesignal.

In various aspects, the generator 1100 may comprise several separatefunctional elements, such as modules and/or blocks, as shown in FIG. 5,a diagram of the surgical system 1000 of FIG. 3. Different functionalelements or modules may be configured for driving the different kinds ofsurgical devices 1104, 1106, 1108. For example an ultrasonic generatormodule may drive an ultrasonic device, such as the ultrasonic device1104. An electrosurgery/RF generator module may drive theelectrosurgical device 1106. The modules may generate respective drivesignals for driving the surgical devices 1104, 1106, 1108. In variousaspects, the ultrasonic generator module and/or the electrosurgery/RFgenerator module each may be formed integrally with the generator 1100.Alternatively, one or more of the modules may be provided as a separatecircuit module electrically coupled to the generator 1100. (The modulesare shown in phantom to illustrate this option.) Also, in some aspects,the electrosurgery/RF generator module may be formed integrally with theultrasonic generator module, or vice versa.

In accordance with the described aspects, the ultrasonic generatormodule may produce a drive signal or signals of particular voltages,currents, and frequencies (e.g. 55,500 cycles per second, or Hz). Thedrive signal or signals may be provided to the ultrasonic device 1104,and specifically to the transducer 1120, which may operate, for example,as described above. In one aspect, the generator 1100 may be configuredto produce a drive signal of a particular voltage, current, and/orfrequency output signal that can be stepped with high resolution,accuracy, and repeatability.

In accordance with the described aspects, the electrosurgery/RFgenerator module may generate a drive signal or signals with outputpower sufficient to perform bipolar electrosurgery using radio frequency(RF) energy. In bipolar electrosurgery applications, the drive signalmay be provided, for example, to the electrodes of the electrosurgicaldevice 1106, for example, as described above. Accordingly, the generator1100 may be configured for therapeutic purposes by applying electricalenergy to the tissue sufficient for treating the tissue (e.g.,coagulation, cauterization, tissue welding, etc.).

The generator 1100 may comprise an input device 2150 (FIG. 8B) located,for example, on a front panel of the generator 1100 console. The inputdevice 2150 may comprise any suitable device that generates signalssuitable for programming the operation of the generator 1100. Inoperation, the user can program or otherwise control operation of thegenerator 1100 using the input device 2150. The input device 2150 maycomprise any suitable device that generates signals that can be used bythe generator (e.g., by one or more processors contained in thegenerator) to control the operation of the generator 1100 (e.g.,operation of the ultrasonic generator module and/or electrosurgery/RFgenerator module). In various aspects, the input device 2150 includesone or more of: buttons, switches, thumbwheels, keyboard, keypad, touchscreen monitor, pointing device, remote connection to a general purposeor dedicated computer. In other aspects, the input device 2150 maycomprise a suitable user interface, such as one or more user interfacescreens displayed on a touch screen monitor, for example. Accordingly,by way of the input device 2150, the user can set or program variousoperating parameters of the generator, such as, for example, current(I), voltage (V), frequency (f), and/or period (T) of a drive signal orsignals generated by the ultrasonic generator module and/orelectrosurgery/RF generator module.

The generator 1100 may also comprise an output device 2140 (FIG. 8B)located, for example, on a front panel of the generator 1100 console.The output device 2140 includes one or more devices for providing asensory feedback to a user. Such devices may comprise, for example,visual feedback devices (e.g., an LCD display screen, LED indicators),audio feedback devices (e.g., a speaker, a buzzer) or tactile feedbackdevices (e.g., haptic actuators).

Although certain modules and/or blocks of the generator 1100 may bedescribed by way of example, it can be appreciated that a greater orlesser number of modules and/or blocks may be used and still fall withinthe scope of the aspects. Further, although various aspects may bedescribed in terms of modules and/or blocks to facilitate description,such modules and/or blocks may be implemented by one or more hardwarecomponents, e.g., processors, Digital Signal Processors (DSPs),Programmable Logic Devices (PLDs), Application Specific IntegratedCircuits (ASICs), circuits, registers and/or software components, e.g.,programs, subroutines, logic and/or combinations of hardware andsoftware components.

In one aspect, the ultrasonic generator drive module andelectrosurgery/RF drive module 1110 (FIG. 3) may comprise one or moreembedded applications implemented as firmware, software, hardware, orany combination thereof. The modules may comprise various executablemodules such as software, programs, data, drivers, application programinterfaces (APIs), and so forth. The firmware may be stored innonvolatile memory (NVM), such as in bit-masked read-only memory (ROM)or flash memory. In various implementations, storing the firmware in ROMmay preserve flash memory. The NVM may comprise other types of memoryincluding, for example, programmable ROM (PROM), erasable programmableROM (EPROM), electrically erasable programmable ROM (EEPROM), or batterybacked random-access memory (RAM) such as dynamic RAM (DRAM),Double-Data-Rate DRAM (DDRAM), and/or synchronous DRAM (SDRAM).

In one aspect, the modules comprise a hardware component implemented asa processor for executing program instructions for monitoring variousmeasurable characteristics of the devices 1104, 1106, 1108 andgenerating a corresponding output drive signal or signals for operatingthe devices 1104, 1106, 1108. In aspects in which the generator 1100 isused in conjunction with the device 1104, the drive signal may drive theultrasonic transducer 1120 in cutting and/or coagulation operatingmodes. Electrical characteristics of the device 1104 and/or tissue maybe measured and used to control operational aspects of the generator1100 and/or provided as feedback to the user. In aspects in which thegenerator 1100 is used in conjunction with the device 1106, the drivesignal may supply electrical energy (e.g., RF energy) to the endeffector 1124 in cutting, coagulation and/or desiccation modes.Electrical characteristics of the device 1106 and/or tissue may bemeasured and used to control operational aspects of the generator 1100and/or provided as feedback to the user. In various aspects, aspreviously discussed, the hardware components may be implemented as DSP,PLD, ASIC, circuits, and/or registers. In one aspect, the processor maybe configured to store and execute computer software programinstructions to generate the step function output signals for drivingvarious components of the devices 1104, 1106, 1108, such as theultrasonic transducer 1120 and the end effectors 1122, 1124, 1125.

An electromechanical ultrasonic system includes an ultrasonictransducer, a waveguide, and an ultrasonic blade. The electromechanicalultrasonic system has an initial resonant frequency defined by thephysical properties of the ultrasonic transducer, the waveguide, and theultrasonic blade. The ultrasonic transducer is excited by an alternatingvoltage V_(g)(t) and current I_(g)(t) signal equal to the resonantfrequency of the electromechanical ultrasonic system. When theelectromechanical ultrasonic system is at resonance, the phasedifference between the voltage V_(g)(t) and current I_(g)(t) signals iszero. Stated another way, at resonance the inductive impedance is equalto the capacitive impedance. As the ultrasonic blade heats up, thecompliance of the ultrasonic blade (modeled as an equivalentcapacitance) causes the resonant frequency of the electromechanicalultrasonic system to shift. Thus, the inductive impedance is no longerequal to the capacitive impedance causing a mismatch between the drivefrequency and the resonant frequency of the electromechanical ultrasonicsystem. The system is now operating “off-resonance.” The mismatchbetween the drive frequency and the resonant frequency is manifested asa phase difference between the voltage V_(g)(t) and current I_(g)(t)signals applied to the ultrasonic transducer. The generator electronicscan easily monitor the phase difference between the voltage V_(g)(t) andcurrent I_(g)(t) signals and can continuously adjust the drive frequencyuntil the phase difference is once again zero. At this point, the newdrive frequency is equal to the new resonant frequency of theelectromechanical ultrasonic system. The change in phase and/orfrequency can be used as an indirect measurement of the ultrasonic bladetemperature.

As shown in FIG. 6, the electromechanical properties of the ultrasonictransducer may be modeled as an equivalent circuit comprising a firstbranch having a static capacitance and a second “motional” branch havinga serially connected inductance, resistance and capacitance that definethe electromechanical properties of a resonator. Known ultrasonicgenerators may include a tuning inductor for tuning out the staticcapacitance at a resonant frequency so that substantially all ofgenerator's drive signal current flows into the motional branch.Accordingly, by using a tuning inductor, the generator's drive signalcurrent represents the motional branch current, and the generator isthus able to control its drive signal to maintain the ultrasonictransducer's resonant frequency. The tuning inductor may also transformthe phase impedance plot of the ultrasonic transducer to improve thegenerator's frequency lock capabilities. However, the tuning inductormust be matched with the specific static capacitance of an ultrasonictransducer at the operational resonance frequency. In other words, adifferent ultrasonic transducer having a different static capacitancerequires a different tuning inductor.

FIG. 6 illustrates an equivalent circuit 1500 of an ultrasonictransducer, such as the ultrasonic transducer 1120, according to oneaspect. The circuit 1500 comprises a first “motional” branch having aserially connected inductance L_(s), resistance R_(s) and capacitanceC_(s) that define the electromechanical properties of the resonator, anda second capacitive branch having a static capacitance C₀. Drive currentI_(g)(t) may be received from a generator at a drive voltage V_(g)(t),with motional current I_(m)(t) flowing through the first branch andcurrent I_(g)(t)-I_(m)(t) flowing through the capacitive branch. Controlof the electromechanical properties of the ultrasonic transducer may beachieved by suitably controlling I_(g)(t) and V_(g)(t). As explainedabove, known generator architectures may include a tuning inductor L_(t)(shown in phantom in FIG. 6) in a parallel resonance circuit for tuningout the static capacitance C₀ at a resonant frequency so thatsubstantially all of the generator's current output I_(g)(t) flowsthrough the motional branch. In this way, control of the motional branchcurrent I_(m)(t) is achieved by controlling the generator current outputI_(g)(t). The tuning inductor L_(t) is specific to the staticcapacitance C₀ of an ultrasonic transducer, however, and a differentultrasonic transducer having a different static capacitance requires adifferent tuning inductor L_(t). Moreover, because the tuning inductorL_(t) is matched to the nominal value of the static capacitance C₀ at asingle resonant frequency, accurate control of the motional branchcurrent I_(m)(t) is assured only at that frequency. As frequency shiftsdown with transducer temperature, accurate control of the motionalbranch current is compromised.

Various aspects of the generator 1100 may not rely on a tuning inductorL_(t) to monitor the motional branch current I_(m)(t). Instead, thegenerator 1100 may use the measured value of the static capacitance C₀in between applications of power for a specific ultrasonic surgicaldevice 1104 (along with drive signal voltage and current feedback data)to determine values of the motional branch current I_(m)(t) on a dynamicand ongoing basis (e.g., in real-time). Such aspects of the generator1100 are therefore able to provide virtual tuning to simulate a systemthat is tuned or resonant with any value of static capacitance C₀ at anyfrequency, and not just at a single resonant frequency dictated by anominal value of the static capacitance C₀.

FIG. 7 is a simplified block diagram of one aspect of the generator 1100for providing inductorless tuning as described above, among otherbenefits. FIGS. 8A-8C illustrate an architecture of the generator 1100of FIG. 7 according to one aspect. With reference to FIG. 7, thegenerator 1100 may comprise a patient isolated stage 1520 incommunication with a non-isolated stage 1540 via a power transformer1560. A secondary winding 1580 of the power transformer 1560 iscontained in the isolated stage 1520 and may comprise a tappedconfiguration (e.g., a center-tapped or non-center tapped configuration)to define drive signal outputs 1600 a, 1600 b, 1600 c for outputtingdrive signals to different surgical devices, such as, for example, anultrasonic surgical device 1104 and an electrosurgical device 1106. Inparticular, drive signal outputs 1600 a, 1600 b, 1600 c may output adrive signal (e.g., a 420V RMS drive signal) to an ultrasonic surgicaldevice 1104, and drive signal outputs 1600 a, 1600 b, 1600 c may outputa drive signal (e.g., a 100V RMS drive signal) to an electrosurgicaldevice 1106, with output 1600 b corresponding to the center tap of thepower transformer 1560. The non-isolated stage 1540 may comprise a poweramplifier 1620 having an output connected to a primary winding 1640 ofthe power transformer 1560. In certain aspects the power amplifier 1620may comprise a push-pull amplifier, for example. The non-isolated stage1540 may further comprise a programmable logic device 1660 for supplyinga digital output to a digital-to-analog converter (DAC) 1680, which inturn supplies a corresponding analog signal to an input of the poweramplifier 1620. In certain aspects the programmable logic device 1660may comprise a field-programmable gate array (FPGA), for example. Theprogrammable logic device 1660, by virtue of controlling the poweramplifier's 1620 input via the DAC 1680, may therefore control any of anumber of parameters (e.g., frequency, waveform shape, waveformamplitude) of drive signals appearing at the drive signal outputs 1600a, 1600 b, 1600 c. In certain aspects and as discussed below, theprogrammable logic device 1660, in conjunction with a processor (e.g.,processor 1740 discussed below), may implement a number of digitalsignal processing (DSP)-based and/or other control algorithms to controlparameters of the drive signals output by the generator 1100.

Power may be supplied to a power rail of the power amplifier 1620 by aswitch-mode regulator 1700. In certain aspects the switch-mode regulator1700 may comprise an adjustable buck regulator 1170, for example. Asdiscussed above, the non-isolated stage 1540 may further comprise aprocessor 1740, which in one aspect may comprise a DSP processor such asan ADSP-21469 SHARC DSP, available from Analog Devices, Norwood, Mass.,for example. In certain aspects the processor 1740 may control operationof the switch-mode power converter 1700 responsive to voltage feedbackdata received from the power amplifier 1620 by the processor 1740 via ananalog-to-digital converter (ADC) 1760. In one aspect, for example, theprocessor 1740 may receive as input, via the ADC 1760, the waveformenvelope of a signal (e.g., an RF signal) being amplified by the poweramplifier 1620. The processor 1740 may then control the switch-moderegulator 1700 (e.g., via a pulse-width modulated (PWM) output) suchthat the rail voltage supplied to the power amplifier 1620 tracks thewaveform envelope of the amplified signal. By dynamically modulating therail voltage of the power amplifier 1620 based on the waveform envelope,the efficiency of the power amplifier 1620 may be significantly improvedrelative to a fixed rail voltage amplifier scheme. The processor 1740may be configured for wired or wireless communication.

In certain aspects and as discussed in further detail in connection withFIGS. 9A-9B, the programmable logic device 1660, in conjunction with theprocessor 1740, may implement a direct digital synthesizer (DDS) controlscheme to control the waveform shape, frequency and/or amplitude ofdrive signals output by the generator 1100. In one aspect, for example,the programmable logic device 1660 may implement a DDS control algorithm2680 (FIG. 9A) by recalling waveform samples stored in adynamically-updated look-up table (LUT), such as a RAM LUT which may beembedded in an FPGA. This control algorithm is particularly useful forultrasonic applications in which an ultrasonic transducer, such as theultrasonic transducer 1120, may be driven by a clean sinusoidal currentat its resonant frequency. Because other frequencies may exciteparasitic resonances, minimizing or reducing the total distortion of themotional branch current may correspondingly minimize or reduceundesirable resonance effects. Because the waveform shape of a drivesignal output by the generator 1100 is impacted by various sources ofdistortion present in the output drive circuit (e.g., the powertransformer 1560, the power amplifier 1620), voltage and currentfeedback data based on the drive signal may be input into an algorithm,such as an error control algorithm implemented by the processor 1740,which compensates for distortion by suitably pre-distorting or modifyingthe waveform samples stored in the LUT on a dynamic, ongoing basis(e.g., in real-time). In one aspect, the amount or degree ofpre-distortion applied to the LUT samples may be based on the errorbetween a computed motional branch current and a desired currentwaveform shape, with the error being determined on a sample-by samplebasis. In this way, the pre-distorted LUT samples, when processedthrough the drive circuit, may result in a motional branch drive signalhaving the desired waveform shape (e.g., sinusoidal) for optimallydriving the ultrasonic transducer. In such aspects, the LUT waveformsamples will therefore not represent the desired waveform shape of thedrive signal, but rather the waveform shape that is required toultimately produce the desired waveform shape of the motional branchdrive signal when distortion effects are taken into account.

The non-isolated stage 1540 may further comprise an ADC 1780 and an ADC1800 coupled to the output of the power transformer 1560 via respectiveisolation transformers 1820, 1840 for respectively sampling the voltageand current of drive signals output by the generator 1100. In certainaspects, the ADCs 1780, 1800 may be configured to sample at high speeds(e.g., 80 Msps) to enable oversampling of the drive signals. In oneaspect, for example, the sampling speed of the ADCs 1780, 1800 mayenable approximately 200× (depending on drive frequency) oversampling ofthe drive signals. In certain aspects, the sampling operations of theADCs 1780, 1800 may be performed by a single ADC receiving input voltageand current signals via a two-way multiplexer. The use of high-speedsampling in aspects of the generator 1100 may enable, among otherthings, calculation of the complex current flowing through the motionalbranch (which may be used in certain aspects to implement DDS-basedwaveform shape control described above), accurate digital filtering ofthe sampled signals, and calculation of real power consumption with ahigh degree of precision. Voltage and current feedback data output bythe ADCs 1780, 1800 may be received and processed (e.g., FIFO buffering,multiplexing) by the programmable logic device 1660 and stored in datamemory for subsequent retrieval by, for example, the processor 1740. Asnoted above, voltage and current feedback data may be used as input toan algorithm for pre-distorting or modifying LUT waveform samples on adynamic and ongoing basis. In certain aspects, this may require eachstored voltage and current feedback data pair to be indexed based on, orotherwise associated with, a corresponding LUT sample that was output bythe programmable logic device 1660 when the voltage and current feedbackdata pair was acquired. Synchronization of the LUT samples and thevoltage and current feedback data in this manner contributes to thecorrect timing and stability of the pre-distortion algorithm.

In certain aspects, the voltage and current feedback data may be used tocontrol the frequency and/or amplitude (e.g., current amplitude) of thedrive signals. In one aspect, for example, voltage and current feedbackdata may be used to determine impedance phase, e.g., the phasedifference between the voltage and current drive signals. The frequencyof the drive signal may then be controlled to minimize or reduce thedifference between the determined impedance phase and an impedance phasesetpoint (e.g., 0°), thereby minimizing or reducing the effects ofharmonic distortion and correspondingly enhancing impedance phasemeasurement accuracy. The determination of phase impedance and afrequency control signal may be implemented in the processor 1740, forexample, with the frequency control signal being supplied as input to aDDS control algorithm implemented by the programmable logic device 1660.

The impedance phase may be determined through Fourier analysis. In oneaspect, the phase difference between the generator voltage V_(g)(t) andgenerator current I_(g)(t) driving signals may be determined using theFast Fourier Transform (FFT) or the Discrete Fourier Transform (DFT) asfollows:

V_(g)(t) = A₁cos (2π f₀t + φ₁) I_(g)(t) = A₂cos (2π f₀t + φ₂)${V_{g}(f)} = {\frac{A_{1}}{2}\left( {{\delta\left( {f - f_{0}} \right)} + {\delta\left( {f + f_{0}} \right)}} \right){\exp\left( {j\; 2\pi\; f\frac{\varphi_{1}}{2\;\pi\; f_{0}}} \right)}}$${I_{g}(f)} = {\frac{A_{2}}{2}\left( {{\delta\left( {f - f_{0}} \right)} + {\delta\left( {f + f_{0}} \right)}} \right){\exp\left( {j\; 2\pi\; f\frac{\varphi_{2}}{2\;\pi\; f_{0}}} \right)}}$

Evaluating the Fourier Transform at the frequency of the sinusoidyields:

$\begin{matrix}{{V_{g}\left( f_{0} \right)} = {\frac{A_{1}}{2}{\delta(0)}{\exp\left( {j\;\varphi_{1}} \right)}}} & {{\arg\;{V\left( f_{0} \right)}} = \varphi_{1}} \\{{I_{g}\left( f_{0} \right)} = {\frac{A_{2}}{2}{\delta(0)}{\exp\left( {j\;\varphi_{2}} \right)}}} & {{\arg\;{I\left( f_{0} \right)}} = \varphi_{2}}\end{matrix}$

Other approaches include weighted least-squares estimation, Kalmanfiltering, and space-vector-based techniques. Virtually all of theprocessing in an FFT or DFT technique may be performed in the digitaldomain with the aid of the 2-channel high speed ADC 1780, 1800, forexample. In one technique, the digital signal samples of the voltage andcurrent signals are Fourier transformed with an FFT or a DFT. The phaseangle φ at any point in time can be calculated by:φ=2πft+φ ₀

where φ is the phase angle, f is the frequency, t is time, and φ₀ is thephase at t=0.

Another technique for determining the phase difference between thevoltage V_(g)(t) and current I_(g)(t) signals is the zero-crossingmethod and produces highly accurate results. For voltage V_(g)(t) andcurrent I_(g)(t) signals having the same frequency, each negative topositive zero-crossing of voltage signal V_(g)(t) triggers the start ofa pulse, while each negative to positive zero-crossing of current signalI_(g)(t) triggers the end of the pulse. The result is a pulse train witha pulse width proportional to the phase angle between the voltage signaland the current signal. In one aspect, the pulse train may be passedthrough an averaging filter to yield a measure of the phase difference.Furthermore, if the positive to negative zero crossings also are used ina similar manner, and the results averaged, any effects of DC andharmonic components can be reduced. In one implementation, the analogvoltage V_(g)(t) and current I_(g)(t) signals are converted to digitalsignals that are high if the analog signal is positive and low if theanalog signal is negative. High accuracy phase estimates require sharptransitions between high and low. In one aspect, a Schmitt trigger alongwith an RC stabilization network may be employed to convert the analogsignals into digital signals. In other aspects, an edge triggered RSflip-flop and ancillary circuitry may be employed. In yet anotheraspect, the zero-crossing technique may employ an eXclusive OR (XOR)gate.

Other techniques for determining the phase difference between thevoltage and current signals include Lissajous figures and monitoring theimage; methods such as the three-voltmeter method, the crossed-coilmethod, vector voltmeter and vector impedance methods; and using phasestandard instruments, phase-locked loops, and other techniques asdescribed in Phase Measurement, Peter O'Shea, 2000 CRC Press LLC,<http://www.engnetbase.com>, which is incorporated herein by reference.

In another aspect, for example, the current feedback data may bemonitored in order to maintain the current amplitude of the drive signalat a current amplitude setpoint. The current amplitude setpoint may bespecified directly or determined indirectly based on specified voltageamplitude and power setpoints. In certain aspects, control of thecurrent amplitude may be implemented by control algorithm, such as, forexample, a proportional-integral-derivative (PID) control algorithm, inthe processor 1740. Variables controlled by the control algorithm tosuitably control the current amplitude of the drive signal may include,for example, the scaling of the LUT waveform samples stored in theprogrammable logic device 1660 and/or the full-scale output voltage ofthe DAC 1680 (which supplies the input to the power amplifier 1620) viaa DAC 1860.

The non-isolated stage 1540 may further comprise a processor 1900 forproviding, among other things, user interface (UI) functionality. In oneaspect, the processor 1900 may comprise an Atmel AT91 SAM9263 processorhaving an ARM 926EJ-S core, available from Atmel Corporation, San Jose,Calif., for example. Examples of UI functionality supported by theprocessor 1900 may include audible and visual user feedback,communication with peripheral devices (e.g., via a Universal Serial Bus(USB) interface), communication with a foot switch 1430, communicationwith an input device 2150 (e.g., a touch screen display) andcommunication with an output device 2140 (e.g., a speaker). Theprocessor 1900 may communicate with the processor 1740 and theprogrammable logic device (e.g., via a serial peripheral interface (SPI)bus). Although the processor 1900 may primarily support UIfunctionality, it may also coordinate with the processor 1740 toimplement hazard mitigation in certain aspects. For example, theprocessor 1900 may be programmed to monitor various aspects of userinput and/or other inputs (e.g., touch screen inputs 2150, foot switch1430 inputs, temperature sensor inputs 2160) and may disable the driveoutput of the generator 1100 when an erroneous condition is detected.

In certain aspects, both the processor 1740 (FIG. 7, 8A) and theprocessor 1900 (FIG. 7, 8B) may determine and monitor the operatingstate of the generator 1100. For processor 1740, the operating state ofthe generator 1100 may dictate, for example, which control and/ordiagnostic processes are implemented by the processor 1740. Forprocessor 1900, the operating state of the generator 1100 may dictate,for example, which elements of a user interface (e.g., display screens,sounds) are presented to a user. The processors 1740, 1900 mayindependently maintain the current operating state of the generator 1100and recognize and evaluate possible transitions out of the currentoperating state. The processor 1740 may function as the master in thisrelationship and determine when transitions between operating states areto occur. The processor 1900 may be aware of valid transitions betweenoperating states and may confirm if a particular transition isappropriate. For example, when the processor 1740 instructs theprocessor 1900 to transition to a specific state, the processor 1900 mayverify that the requested transition is valid. In the event that arequested transition between states is determined to be invalid by theprocessor 1900, the processor 1900 may cause the generator 1100 to entera failure mode.

The non-isolated stage 1540 may further comprise a controller 1960 (FIG.7, 8B) for monitoring input devices 2150 (e.g., a capacitive touchsensor used for turning the generator 1100 on and off, a capacitivetouch screen). In certain aspects, the controller 1960 may comprise atleast one processor and/or other controller device in communication withthe processor 1900. In one aspect, for example, the controller 1960 maycomprise a processor (e.g., a Mega168 8-bit controller available fromAtmel) configured to monitor user input provided via one or morecapacitive touch sensors. In one aspect, the controller 1960 maycomprise a touch screen controller (e.g., a QT5480 touch screencontroller available from Atmel) to control and manage the acquisitionof touch data from a capacitive touch screen.

In certain aspects, when the generator 1100 is in a “power off” state,the controller 1960 may continue to receive operating power (e.g., via aline from a power supply of the generator 1100, such as the power supply2110 (FIG. 7) discussed below). In this way, the controller 1960 maycontinue to monitor an input device 2150 (e.g., a capacitive touchsensor located on a front panel of the generator 1100) for turning thegenerator 1100 on and off. When the generator 1100 is in the “power off”state, the controller 1960 may wake the power supply (e.g., enableoperation of one or more DC/DC voltage converters 2130 (FIG. 7) of thepower supply 2110) if activation of the “on/off” input device 2150 by auser is detected. The controller 1960 may therefore initiate a sequencefor transitioning the generator 1100 to a “power on” state. Conversely,the controller 1960 may initiate a sequence for transitioning thegenerator 1100 to the “power off” state if activation of the “on/off”input device 2150 is detected when the generator 1100 is in the “poweron” state. In certain aspects, for example, the controller 1960 mayreport activation of the “on/off” input device 2150 to the processor1900, which in turn implements the necessary process sequence fortransitioning the generator 1100 to the “power off” state. In suchaspects, the controller 1960 may have no independent ability for causingthe removal of power from the generator 1100 after its “power on” statehas been established.

In certain aspects, the controller 1960 may cause the generator 1100 toprovide audible or other sensory feedback for alerting the user that a“power on” or “power off” sequence has been initiated. Such an alert maybe provided at the beginning of a “power on” or “power off” sequence andprior to the commencement of other processes associated with thesequence.

In certain aspects, the isolated stage 1520 may comprise an instrumentinterface circuit 1980 to, for example, provide a communicationinterface between a control circuit of a surgical device (e.g., acontrol circuit comprising handpiece switches) and components of thenon-isolated stage 1540, such as, for example, the programmable logicdevice 1660, the processor 1740 and/or the processor 1900. Theinstrument interface circuit 1980 may exchange information withcomponents of the non-isolated stage 1540 via a communication link thatmaintains a suitable degree of electrical isolation between the stages1520, 1540, such as, for example, an infrared (IR)-based communicationlink. Power may be supplied to the instrument interface circuit 1980using, for example, a low-dropout voltage regulator powered by anisolation transformer driven from the non-isolated stage 1540.

In one aspect, the instrument interface circuit 1980 may comprise aprogrammable logic device 2000 (e.g., an FPGA) in communication with asignal conditioning circuit 2020 (FIG. 7 and FIG. 8C). The signalconditioning circuit 2020 may be configured to receive a periodic signalfrom the programmable logic device 2000 (e.g., a 2 kHz square wave) togenerate a bipolar interrogation signal having an identical frequency.The interrogation signal may be generated, for example, using a bipolarcurrent source fed by a differential amplifier. The interrogation signalmay be communicated to a surgical device control circuit (e.g., by usinga conductive pair in a cable that connects the generator 1100 to thesurgical device) and monitored to determine a state or configuration ofthe control circuit. For example, the control circuit may comprise anumber of switches, resistors and/or diodes to modify one or morecharacteristics (e.g., amplitude, rectification) of the interrogationsignal such that a state or configuration of the control circuit isuniquely discernible based on the one or more characteristics. In oneaspect, for example, the signal conditioning circuit 2020 may comprisean ADC for generating samples of a voltage signal appearing acrossinputs of the control circuit resulting from passage of interrogationsignal therethrough. The programmable logic device 2000 (or a componentof the non-isolated stage 1540) may then determine the state orconfiguration of the control circuit based on the ADC samples.

In one aspect, the instrument interface circuit 1980 may comprise afirst data circuit interface 2040 to enable information exchange betweenthe programmable logic device 2000 (or other element of the instrumentinterface circuit 1980) and a first data circuit disposed in orotherwise associated with a surgical device. In certain aspects, forexample, a first data circuit 2060 may be disposed in a cable integrallyattached to a surgical device handpiece, or in an adaptor forinterfacing a specific surgical device type or model with the generator1100. In certain aspects, the first data circuit may comprise anon-volatile storage device, such as an electrically erasableprogrammable read-only memory (EEPROM) device. In certain aspects andreferring again to FIG. 7, the first data circuit interface 2040 may beimplemented separately from the programmable logic device 2000 andcomprise suitable circuitry (e.g., discrete logic devices, a processor)to enable communication between the programmable logic device 2000 andthe first data circuit. In other aspects, the first data circuitinterface 2040 may be integral with the programmable logic device 2000.

In certain aspects, the first data circuit 2060 may store informationpertaining to the particular surgical device with which it isassociated. Such information may include, for example, a model number, aserial number, a number of operations in which the surgical device hasbeen used, and/or any other type of information. This information may beread by the instrument interface circuit 1980 (e.g., by the programmablelogic device 2000), transferred to a component of the non-isolated stage1540 (e.g., to programmable logic device 1660, processor 1740 and/orprocessor 1900) for presentation to a user via an output device 2140and/or for controlling a function or operation of the generator 1100.Additionally, any type of information may be communicated to first datacircuit 2060 for storage therein via the first data circuit interface2040 (e.g., using the programmable logic device 2000). Such informationmay comprise, for example, an updated number of operations in which thesurgical device has been used and/or dates and/or times of its usage.

As discussed previously, a surgical instrument may be detachable from ahandpiece (e.g., instrument 1106 may be detachable from handpiece 1107)to promote instrument interchangeability and/or disposability. In suchcases, known generators may be limited in their ability to recognizeparticular instrument configurations being used and to optimize controland diagnostic processes accordingly. The addition of readable datacircuits to surgical device instruments to address this issue isproblematic from a compatibility standpoint, however. For example, itmay be impractical to design a surgical device to maintain backwardcompatibility with generators that lack the requisite data readingfunctionality due to, for example, differing signal schemes, designcomplexity and cost. Other aspects of instruments address these concernsby using data circuits that may be implemented in existing surgicalinstruments economically and with minimal design changes to preservecompatibility of the surgical devices with current generator platforms.

Additionally, aspects of the generator 1100 may enable communicationwith instrument-based data circuits. For example, the generator 1100 maybe configured to communicate with a second data circuit (e.g., a datacircuit) contained in an instrument (e.g., instrument 1104, 1106 or1108) of a surgical device. The instrument interface circuit 1980 maycomprise a second data circuit interface 2100 to enable thiscommunication. In one aspect, the second data circuit interface 2100 maycomprise a tri-state digital interface, although other interfaces mayalso be used. In certain aspects, the second data circuit may generallybe any circuit for transmitting and/or receiving data. In one aspect,for example, the second data circuit may store information pertaining tothe particular surgical instrument with which it is associated. Suchinformation may include, for example, a model number, a serial number, anumber of operations in which the surgical instrument has been used,and/or any other type of information. Additionally or alternatively, anytype of information may be communicated to the second data circuit forstorage therein via the second data circuit interface 2100 (e.g., usingthe programmable logic device 2000). Such information may comprise, forexample, an updated number of operations in which the instrument hasbeen used and/or dates and/or times of its usage. In certain aspects,the second data circuit may transmit data acquired by one or moresensors (e.g., an instrument-based temperature sensor). In certainaspects, the second data circuit may receive data from the generator1100 and provide an indication to a user (e.g., an LED indication orother visible indication) based on the received data.

In certain aspects, the second data circuit and the second data circuitinterface 2100 may be configured such that communication between theprogrammable logic device 2000 and the second data circuit can beeffected without the need to provide additional conductors for thispurpose (e.g., dedicated conductors of a cable connecting a handpiece tothe generator 1100). In one aspect, for example, information may becommunicated to and from the second data circuit using a one-wire buscommunication scheme implemented on existing cabling, such as one of theconductors used transmit interrogation signals from the signalconditioning circuit 2020 to a control circuit in a handpiece. In thisway, design changes or modifications to the surgical device that mightotherwise be necessary are minimized or reduced. Moreover, becausedifferent types of communications can be implemented over a commonphysical channel (either with or without frequency-band separation), thepresence of a second data circuit may be “invisible” to generators thatdo not have the requisite data reading functionality, thus enablingbackward compatibility of the surgical device instrument.

In certain aspects, the isolated stage 1520 may comprise at least oneblocking capacitor 2960-1 (FIG. 8C) connected to the drive signal output1600 b to prevent passage of DC current to a patient. A single blockingcapacitor may be required to comply with medical regulations orstandards, for example. While failure in single-capacitor designs isrelatively uncommon, such failure may nonetheless have negativeconsequences. In one aspect, a second blocking capacitor 2960-2 may beprovided in series with the blocking capacitor 2960-1, with currentleakage from a point between the blocking capacitors 2960-1, 2960-2being monitored by, for example, an ADC 2980 for sampling a voltageinduced by leakage current. The samples may be received by theprogrammable logic device 2000, for example. Based on changes in theleakage current (as indicated by the voltage samples in the aspect ofFIG. 7), the generator 1100 may determine when at least one of theblocking capacitors 2960-1, 2960-2 has failed. Accordingly, the aspectof FIG. 7 may provide a benefit over single-capacitor designs having asingle point of failure.

In certain aspects, the non-isolated stage 1540 may comprise a powersupply 2110 for outputting DC power at a suitable voltage and current.The power supply may comprise, for example, a 400 W power supply foroutputting a 48 VDC system voltage. As discussed above, the power supply2110 may further comprise one or more DC/DC voltage converters 2130 forreceiving the output of the power supply to generate DC outputs at thevoltages and currents required by the various components of thegenerator 1100. As discussed above in connection with the controller1960, one or more of the DC/DC voltage converters 2130 may receive aninput from the controller 1960 when activation of the “on/off” inputdevice 2150 by a user is detected by the controller 1960 to enableoperation of, or wake, the DC/DC voltage converters 2130.

FIGS. 9A-9B illustrate certain functional and structural aspects of oneaspect of the generator 1100. Feedback indicating current and voltageoutput from the secondary winding 1580 of the power transformer 1560 isreceived by the ADCs 1780, 1800, respectively. As shown, the ADCs 1780,1800 may be implemented as a 2-channel ADC and may sample the feedbacksignals at a high speed (e.g., 80 Msps) to enable oversampling (e.g.,approximately 200× oversampling) of the drive signals. The current andvoltage feedback signals may be suitably conditioned in the analogdomain (e.g., amplified, filtered) prior to processing by the ADCs 1780,1800. Current and voltage feedback samples from the ADCs 1780, 1800 maybe individually buffered and subsequently multiplexed or interleavedinto a single data stream within block 2120 of the programmable logicdevice 1660. In the aspect of FIGS. 9A-9B, the programmable logic device1660 comprises an FPGA.

The multiplexed current and voltage feedback samples may be received bya parallel data acquisition port (PDAP) implemented within block 2144 ofthe processor 1740. The PDAP may comprise a packing unit forimplementing any of a number of methodologies for correlating themultiplexed feedback samples with a memory address. In one aspect, forexample, feedback samples corresponding to a particular LUT sampleoutput by the programmable logic device 1660 may be stored at one ormore memory addresses that are correlated or indexed with the LUTaddress of the LUT sample. In another aspect, feedback samplescorresponding to a particular LUT sample output by the programmablelogic device 1660 may be stored, along with the LUT address of the LUTsample, at a common memory location. In any event, the feedback samplesmay be stored such that the address of the LUT sample from which aparticular set of feedback samples originated may be subsequentlyascertained. As discussed above, synchronization of the LUT sampleaddresses and the feedback samples in this way contributes to thecorrect timing and stability of the pre-distortion algorithm. A directmemory access (DMA) controller implemented at block 2166 of theprocessor 1740 may store the feedback samples (and any LUT sampleaddress data, where applicable) at a designated memory location 2180 ofthe processor 1740 (e.g., internal RAM).

Block 2200 of the processor 1740 may implement a pre-distortionalgorithm for pre-distorting or modifying the LUT samples stored in theprogrammable logic device 1660 on a dynamic, ongoing basis. As discussedabove, pre-distortion of the LUT samples may compensate for varioussources of distortion present in the output drive circuit of thegenerator 1100. The pre-distorted LUT samples, when processed throughthe drive circuit, will therefore result in a drive signal having thedesired waveform shape (e.g., sinusoidal) for optimally driving theultrasonic transducer.

At block 2220 of the pre-distortion algorithm, the current through themotional branch of the ultrasonic transducer is determined. The motionalbranch current may be determined using Kirchhoff's Current Law based on,for example, the current and voltage feedback samples stored at memorylocation 2180 (which, when suitably scaled, may be representative ofI_(g) and V_(g) in the model of FIG. 6 discussed above), a value of theultrasonic transducer static capacitance C₀ (measured or known a priori)and a known value of the drive frequency. A motional branch currentsample for each set of stored current and voltage feedback samplesassociated with a LUT sample may be determined.

At block 2240 of the pre-distortion algorithm, each motional branchcurrent sample determined at block 2220 is compared to a sample of adesired current waveform shape to determine a difference, or sampleamplitude error, between the compared samples. For this determination,the sample of the desired current waveform shape may be supplied, forexample, from a waveform shape LUT 2260 containing amplitude samples forone cycle of a desired current waveform shape. The particular sample ofthe desired current waveform shape from the LUT 2260 used for thecomparison may be dictated by the LUT sample address associated with themotional branch current sample used in the comparison. Accordingly, theinput of the motional branch current to block 2240 may be synchronizedwith the input of its associated LUT sample address to block 2240. TheLUT samples stored in the programmable logic device 1660 and the LUTsamples stored in the waveform shape LUT 2260 may therefore be equal innumber. In certain aspects, the desired current waveform shaperepresented by the LUT samples stored in the waveform shape LUT 2260 maybe a fundamental sine wave. Other waveform shapes may be desirable. Forexample, it is contemplated that a fundamental sine wave for drivingmain longitudinal motion of an ultrasonic transducer superimposed withone or more other drive signals at other frequencies, such as a thirdorder harmonic for driving at least two mechanical resonances forbeneficial vibrations of transverse or other modes, could be used.

Each value of the sample amplitude error determined at block 2240 may betransmitted to the LUT of the programmable logic device 1660 (shown atblock 2280 in FIG. 9A) along with an indication of its associated LUTaddress. Based on the value of the sample amplitude error and itsassociated address (and, optionally, values of sample amplitude errorfor the same LUT address previously received), the LUT 2280 (or othercontrol block of the programmable logic device 1660) may pre-distort ormodify the value of the LUT sample stored at the LUT address such thatthe sample amplitude error is reduced or minimized. It will beappreciated that such pre-distortion or modification of each LUT samplein an iterative manner across the entire range of LUT addresses willcause the waveform shape of the generator's output current to match orconform to the desired current waveform shape represented by the samplesof the waveform shape LUT 2260.

Current and voltage amplitude measurements, power measurements andimpedance measurements may be determined at block 2300 of the processor1740 based on the current and voltage feedback samples stored at memorylocation 2180. Prior to the determination of these quantities, thefeedback samples may be suitably scaled and, in certain aspects,processed through a suitable filter 2320 to remove noise resulting from,for example, the data acquisition process and induced harmoniccomponents. The filtered voltage and current samples may thereforesubstantially represent the fundamental frequency of the generator'sdrive output signal. In certain aspects, the filter 2320 may be a finiteimpulse response (FIR) filter applied in the frequency domain. Suchaspects may use the Fast Fourier Transform (FFT) of the output drivesignal current and voltage signals. In certain aspects, the resultingfrequency spectrum may be used to provide additional generatorfunctionality. In one aspect, for example, the ratio of the secondand/or third order harmonic component relative to the fundamentalfrequency component may be used as a diagnostic indicator.

At block 2340 (FIG. 9B), a root mean square (RMS) calculation may beapplied to a sample size of the current feedback samples representing anintegral number of cycles of the drive signal to generate a measurementI_(rms) representing the drive signal output current.

At block 2360, a root mean square (RMS) calculation may be applied to asample size of the voltage feedback samples representing an integralnumber of cycles of the drive signal to determine a measurement V_(rms)representing the drive signal output voltage.

At block 2380, the current and voltage feedback samples may bemultiplied point by point, and a mean calculation is applied to samplesrepresenting an integral number of cycles of the drive signal todetermine a measurement P_(r) of the generator's real output power.

At block 2400, measurement P_(a) of the generator's apparent outputpower may be determined as the product V_(rms)·I_(rms).

At block 2420, measurement Z_(m) of the load impedance magnitude may bedetermined as the quotient V_(rms)/I_(rms).

In certain aspects, the quantities I_(rms), V_(rms), P_(r), P_(a) andZ_(m) determined at blocks 2340, 2360, 2380, 2400 and 2420 may be usedby the generator 1100 to implement any of a number of control and/ordiagnostic processes. In certain aspects, any of these quantities may becommunicated to a user via, for example, an output device 2140 integralwith the generator 1100 or an output device 2140 connected to thegenerator 1100 through a suitable communication interface (e.g., a USBinterface). Various diagnostic processes may include, withoutlimitation, handpiece integrity, instrument integrity, instrumentattachment integrity, instrument overload, approaching instrumentoverload, frequency lock failure, over-voltage condition, over-currentcondition, over-power condition, voltage sense failure, current sensefailure, audio indication failure, visual indication failure, shortcircuit condition, power delivery failure, or blocking capacitorfailure, for example.

Block 2440 of the processor 1740 may implement a phase control algorithmfor determining and controlling the impedance phase of an electricalload (e.g., the ultrasonic transducer) driven by the generator 1100. Asdiscussed above, by controlling the frequency of the drive signal tominimize or reduce the difference between the determined impedance phaseand an impedance phase setpoint (e.g., 0°), the effects of harmonicdistortion may be minimized or reduced, and the accuracy of the phasemeasurement increased.

The phase control algorithm receives as input the current and voltagefeedback samples stored in the memory location 2180. Prior to their usein the phase control algorithm, the feedback samples may be suitablyscaled and, in certain aspects, processed through a suitable filter 2460(which may be identical to filter 2320) to remove noise resulting fromthe data acquisition process and induced harmonic components, forexample. The filtered voltage and current samples may thereforesubstantially represent the fundamental frequency of the generator'sdrive output signal.

At block 2480 of the phase control algorithm, the current through themotional branch of the ultrasonic transducer is determined. Thisdetermination may be identical to that described above in connectionwith block 2220 of the pre-distortion algorithm. The output of block2480 may thus be, for each set of stored current and voltage feedbacksamples associated with a LUT sample, a motional branch current sample.

At block 2500 of the phase control algorithm, impedance phase isdetermined based on the synchronized input of motional branch currentsamples determined at block 2480 and corresponding voltage feedbacksamples. In certain aspects, the impedance phase is determined as theaverage of the impedance phase measured at the rising edge of thewaveforms and the impedance phase measured at the falling edge of thewaveforms.

At block 2520 of the of the phase control algorithm, the value of theimpedance phase determined at block 2220 is compared to phase setpoint2540 to determine a difference, or phase error, between the comparedvalues.

At block 2560 (FIG. 9A) of the phase control algorithm, based on a valueof phase error determined at block 2520 and the impedance magnitudedetermined at block 2420, a frequency output for controlling thefrequency of the drive signal is determined. The value of the frequencyoutput may be continuously adjusted by the block 2560 and transferred toa DDS control block 2680 (discussed below) in order to maintain theimpedance phase determined at block 2500 at the phase setpoint (e.g.,zero phase error). In certain aspects, the impedance phase may beregulated to a 0° phase setpoint. In this way, any harmonic distortionwill be centered about the crest of the voltage waveform, enhancing theaccuracy of phase impedance determination.

Block 2580 of the processor 1740 may implement an algorithm formodulating the current amplitude of the drive signal in order to controlthe drive signal current, voltage and power in accordance with userspecified setpoints, or in accordance with requirements specified byother processes or algorithms implemented by the generator 1100. Controlof these quantities may be realized, for example, by scaling the LUTsamples in the LUT 2280 and/or by adjusting the full-scale outputvoltage of the DAC 1680 (which supplies the input to the power amplifier1620) via a DAC 1860. Block 2600 (which may be implemented as a PIDcontroller in certain aspects) may receive, as input, current feedbacksamples (which may be suitably scaled and filtered) from the memorylocation 2180. The current feedback samples may be compared to a“current demand” I_(d) value dictated by the controlled variable (e.g.,current, voltage or power) to determine if the drive signal is supplyingthe necessary current. In aspects in which drive signal current is thecontrol variable, the current demand I_(d) may be specified directly bya current setpoint 2620A (I_(sp)). For example, an RMS value of thecurrent feedback data (determined as in block 2340) may be compared touser-specified RMS current setpoint I_(sp) to determine the appropriatecontroller action. If, for example, the current feedback data indicatesan RMS value less than the current setpoint I_(sp), LUT scaling and/orthe full-scale output voltage of the DAC 1680 may be adjusted by theblock 2600 such that the drive signal current is increased. Conversely,block 2600 may adjust LUT scaling and/or the full-scale output voltageof the DAC 1680 to decrease the drive signal current when the currentfeedback data indicates an RMS value greater than the current setpointI_(sp).

In aspects in which the drive signal voltage is the control variable,the current demand I_(d) may be specified indirectly, for example, basedon the current required to maintain a desired voltage setpoint 2620B(I_(sp)) given the load impedance magnitude Z_(m) measured at block 2420(e.g. I_(d)=V_(sp)/Z_(m)). Similarly, in aspects in which drive signalpower is the control variable, the current demand I_(d) may be specifiedindirectly, for example, based on the current required to maintain adesired power setpoint 2620C (P_(sp)) given the voltage V_(rms) measuredat blocks 2360 (e.g. I_(d)=P_(sp)/V_(rms)).

Block 2680 (FIG. 9A) may implement a DDS control algorithm forcontrolling the drive signal by recalling LUT samples stored in the LUT2280. In certain aspects, the DDS control algorithm may be anumerically-controlled oscillator (NCO) algorithm for generating samplesof a waveform at a fixed clock rate using a point (memorylocation)-skipping technique. The NCO algorithm may implement a phaseaccumulator, or frequency-to-phase converter, that functions as anaddress pointer for recalling LUT samples from the LUT 2280. In oneaspect, the phase accumulator may be a D step size, modulo N phaseaccumulator, where D is a positive integer representing a frequencycontrol value, and N is the number of LUT samples in the LUT 2280. Afrequency control value of D=1, for example, may cause the phaseaccumulator to sequentially point to every address of the LUT 2280,resulting in a waveform output replicating the waveform stored in theLUT 2280. When D>1, the phase accumulator may skip addresses in the LUT2280, resulting in a waveform output having a higher frequency.Accordingly, the frequency of the waveform generated by the DDS controlalgorithm may therefore be controlled by suitably varying the frequencycontrol value. In certain aspects, the frequency control value may bedetermined based on the output of the phase control algorithmimplemented at block 2440. The output of block 2680 may supply the inputof DAC 1680, which in turn supplies a corresponding analog signal to aninput of the power amplifier 1620.

Block 2700 of the processor 1740 may implement a switch-mode convertercontrol algorithm for dynamically modulating the rail voltage of thepower amplifier 1620 based on the waveform envelope of the signal beingamplified, thereby improving the efficiency of the power amplifier 1620.In certain aspects, characteristics of the waveform envelope may bedetermined by monitoring one or more signals contained in the poweramplifier 1620. In one aspect, for example, characteristics of thewaveform envelope may be determined by monitoring the minima of a drainvoltage (e.g., a MOSFET drain voltage) that is modulated in accordancewith the envelope of the amplified signal. A minima voltage signal maybe generated, for example, by a voltage minima detector coupled to thedrain voltage. The minima voltage signal may be sampled by ADC 1760,with the output minima voltage samples being received at block 2720 ofthe switch-mode converter control algorithm. Based on the values of theminima voltage samples, block 2740 may control a PWM signal output by aPWM generator 2760, which, in turn, controls the rail voltage suppliedto the power amplifier 1620 by the switch-mode regulator 1700. Incertain aspects, as long as the values of the minima voltage samples areless than a minima target 2780 input into block 2720, the rail voltagemay be modulated in accordance with the waveform envelope ascharacterized by the minima voltage samples. When the minima voltagesamples indicate low envelope power levels, for example, block 2740 maycause a low rail voltage to be supplied to the power amplifier 1620,with the full rail voltage being supplied only when the minima voltagesamples indicate maximum envelope power levels. When the minima voltagesamples fall below the minima target 2780, block 2740 may cause the railvoltage to be maintained at a minimum value suitable for ensuring properoperation of the power amplifier 1620.

FIG. 10 illustrates a control circuit 500 configured to control aspectsof the surgical instrument or tool according to one aspect of thisdisclosure. The control circuit 500 can be configured to implementvarious processes described herein. The control circuit 500 may comprisea microcontroller comprising one or more processors 502 (e.g.,microprocessor, microcontroller) coupled to at least one memory circuit504. The memory circuit 504 stores machine-executable instructions that,when executed by the processor 502, cause the processor 502 to executemachine instructions to implement various processes described herein.The processor 502 may be any one of a number of single-core or multicoreprocessors known in the art. The memory circuit 504 may comprisevolatile and non-volatile storage media. The processor 502 may includean instruction processing unit 506 and an arithmetic unit 508. Theinstruction processing unit may be configured to receive instructionsfrom the memory circuit 504 of this disclosure.

FIG. 11 illustrates a combinational logic circuit 510 configured tocontrol aspects of the surgical instrument or tool according to oneaspect of this disclosure. The combinational logic circuit 510 can beconfigured to implement various processes described herein. Thecombinational logic circuit 510 may comprise a finite state machinecomprising a combinational logic 512 configured to receive dataassociated with the surgical instrument or tool at an input 514, processthe data by the combinational logic 512, and provide an output 516.

FIG. 12 illustrates a sequential logic circuit 520 configured to controlaspects of the surgical instrument or tool according to one aspect ofthis disclosure. The sequential logic circuit 520 or the combinationallogic 522 can be configured to implement various processes describedherein. The sequential logic circuit 520 may comprise a finite statemachine. The sequential logic circuit 520 may comprise a combinationallogic 522, at least one memory circuit 524, and a clock 529, forexample. The at least one memory circuit 524 can store a current stateof the finite state machine. In certain instances, the sequential logiccircuit 520 may be synchronous or asynchronous. The combinational logic522 is configured to receive data associated with the surgicalinstrument or tool from an input 526, process the data by thecombinational logic 522, and provide an output 528. In other aspects,the circuit may comprise a combination of a processor (e.g., processor502, FIG. 10) and a finite state machine to implement various processesherein. In other aspects, the finite state machine may comprise acombination of a combinational logic circuit (e.g., combinational logiccircuit 510, FIG. 11) and the sequential logic circuit 520.

In one aspect, the ultrasonic or high-frequency current generators ofthe surgical system 1000 may be configured to generate the electricalsignal waveform digitally such that the desired using a predeterminednumber of phase points stored in a lookup table to digitize the waveshape. The phase points may be stored in a table defined in a memory, afield programmable gate array (FPGA), or any suitable non-volatilememory. FIG. 13 illustrates one aspect of a fundamental architecture fora digital synthesis circuit such as a direct digital synthesis (DDS)circuit 4100 configured to generate a plurality of wave shapes for theelectrical signal waveform. The generator software and digital controlsmay command the FPGA to scan the addresses in the lookup table 4104which in turn provides varying digital input values to a DAC circuit4108 that feeds a power amplifier. The addresses may be scannedaccording to a frequency of interest. Using such a lookup table 4104enables generating various types of wave shapes that can be fed intotissue or into a transducer, an RF electrode, multiple transducerssimultaneously, multiple RF electrodes simultaneously, or a combinationof RF and ultrasonic instruments. Furthermore, multiple lookup tables4104 that represent multiple wave shapes can be created, stored, andapplied to tissue from a generator.

The waveform signal may be configured to control at least one of anoutput current, an output voltage, or an output power of an ultrasonictransducer and/or an RF electrode, or multiples thereof (e.g. two ormore ultrasonic transducers and/or two or more RF electrodes). Further,where the surgical instrument comprises an ultrasonic components, thewaveform signal may be configured to drive at least two vibration modesof an ultrasonic transducer of the at least one surgical instrument.Accordingly, a generator may be configured to provide a waveform signalto at least one surgical instrument wherein the waveform signalcorresponds to at least one wave shape of a plurality of wave shapes ina table. Further, the waveform signal provided to the two surgicalinstruments may comprise two or more wave shapes. The table may compriseinformation associated with a plurality of wave shapes and the table maybe stored within the generator. In one aspect or example, the table maybe a direct digital synthesis table, which may be stored in an FPGA ofthe generator. The table may be addressed by anyway that is convenientfor categorizing wave shapes. According to one aspect, the table, whichmay be a direct digital synthesis table, is addressed according to afrequency of the waveform signal. Additionally, the informationassociated with the plurality of wave shapes may be stored as digitalinformation in the table.

The analog electrical signal waveform may be configured to control atleast one of an output current, an output voltage, or an output power ofan ultrasonic transducer and/or an RF electrode, or multiples thereof(e.g., two or more ultrasonic transducers and/or two or more RFelectrodes). Further, where the surgical instrument comprises ultrasoniccomponents, the analog electrical signal waveform may be configured todrive at least two vibration modes of an ultrasonic transducer of the atleast one surgical instrument. Accordingly, the generator circuit may beconfigured to provide an analog electrical signal waveform to at leastone surgical instrument wherein the analog electrical signal waveformcorresponds to at least one wave shape of a plurality of wave shapesstored in a lookup table 4104. Further, the analog electrical signalwaveform provided to the two surgical instruments may comprise two ormore wave shapes. The lookup table 4104 may comprise informationassociated with a plurality of wave shapes and the lookup table 4104 maybe stored either within the generator circuit or the surgicalinstrument. In one aspect or example, the lookup table 4104 may be adirect digital synthesis table, which may be stored in an FPGA of thegenerator circuit or the surgical instrument. The lookup table 4104 maybe addressed by anyway that is convenient for categorizing wave shapes.According to one aspect, the lookup table 4104, which may be a directdigital synthesis table, is addressed according to a frequency of thedesired analog electrical signal waveform. Additionally, the informationassociated with the plurality of wave shapes may be stored as digitalinformation in the lookup table 4104.

With the widespread use of digital techniques in instrumentation andcommunications systems, a digitally-controlled method of generatingmultiple frequencies from a reference frequency source has evolved andis referred to as direct digital synthesis. The basic architecture isshown in FIG. 13. In this simplified block diagram, a DDS circuit iscoupled to a processor, controller, or a logic device of the generatorcircuit and to a memory circuit located in the generator circuit of thesurgical system 1000. The DDS circuit 4100 comprises an address counter4102, lookup table 4104, a register 4106, a DAC circuit 4108, and afilter 4112. A stable clock f_(c) is received by the address counter4102 and the register 4106 drives a programmable-read-only-memory (PROM)which stores one or more integral number of cycles of a sinewave (orother arbitrary waveform) in a lookup table 4104. As the address counter4102 steps through memory locations, values stored in the lookup table4104 are written to the register 4106, which is coupled to the DACcircuit 4108. The corresponding digital amplitude of the signal at thememory location of the lookup table 4104 drives the DAC circuit 4108,which in turn generates an analog output signal 4110. The spectralpurity of the analog output signal 4110 is determined primarily by theDAC circuit 4108. The phase noise is basically that of the referenceclock f_(c). The first analog output signal 4110 output from the DACcircuit 4108 is filtered by the filter 4112 and a second analog outputsignal 4114 output by the filter 4112 is provided to an amplifier havingan output coupled to the output of the generator circuit. The secondanalog output signal has a frequency f_(out).

Because the DDS circuit 4100 is a sampled data system, issues involvedin sampling must be considered: quantization noise, aliasing, filtering,etc. For instance, the higher order harmonics of the DAC circuit 4108output frequencies fold back into the Nyquist bandwidth, making themunfilterable, whereas, the higher order harmonics of the output ofphase-locked-loop (PLL) based synthesizers can be filtered. The lookuptable 4104 contains signal data for an integral number of cycles. Thefinal output frequency f_(out) can be changed changing the referenceclock frequency f_(c) or by reprogramming the PROM.

The DDS circuit 4100 may comprise multiple lookup tables 4104 where thelookup table 4104 stores a waveform represented by a predeterminednumber of samples, wherein the samples define a predetermined shape ofthe waveform. Thus multiple waveforms having a unique shape can bestored in multiple lookup tables 4104 to provide different tissuetreatments based on instrument settings or tissue feedback. Examples ofwaveforms include high crest factor RF electrical signal waveforms forsurface tissue coagulation, low crest factor RF electrical signalwaveform for deeper tissue penetration, and electrical signal waveformsthat promote efficient touch-up coagulation. In one aspect, the DDScircuit 4100 can create multiple wave shape lookup tables 4104 andduring a tissue treatment procedure (e.g., “on-the-fly” or in virtualreal time based on user or sensor inputs) switch between different waveshapes stored in separate lookup tables 4104 based on the tissue effectdesired and/or tissue feedback.

Accordingly, switching between wave shapes can be based on tissueimpedance and other factors, for example. In other aspects, the lookuptables 4104 can store electrical signal waveforms shaped to maximize thepower delivered into the tissue per cycle (i.e., trapezoidal or squarewave). In other aspects, the lookup tables 4104 can store wave shapessynchronized in such way that they make maximizing power delivery by themultifunction surgical instrument of surgical system 1000 whiledelivering RF and ultrasonic drive signals. In yet other aspects, thelookup tables 4104 can store electrical signal waveforms to driveultrasonic and RF therapeutic, and/or sub-therapeutic, energysimultaneously while maintaining ultrasonic frequency lock. Custom waveshapes specific to different instruments and their tissue effects can bestored in the non-volatile memory of the generator circuit or in thenon-volatile memory (e.g., EEPROM) of the surgical system 1000 and befetched upon connecting the multifunction surgical instrument to thegenerator circuit. An example of an exponentially damped sinusoid, asused in many high crest factor “coagulation” waveforms is shown in FIG.15.

A more flexible and efficient implementation of the DDS circuit 4100employs a digital circuit called a Numerically Controlled Oscillator(NCO). A block diagram of a more flexible and efficient digitalsynthesis circuit such as a DDS circuit 4200 is shown in FIG. 14. Inthis simplified block diagram, a DDS circuit 4200 is coupled to aprocessor, controller, or a logic device of the generator and to amemory circuit located either in the generator or in any of the surgicalinstruments of surgical system 1000. The DDS circuit 4200 comprises aload register 4202, a parallel delta phase register 4204, an addercircuit 4216, a phase register 4208, a lookup table 4210(phase-to-amplitude converter), a DAC circuit 4212, and a filter 4214.The adder circuit 4216 and the phase register 4208 form part of a phaseaccumulator 4206. A clock frequency f_(c) is applied to the phaseregister 4208 and a DAC circuit 4212. The load register 4202 receives atuning word that specifies output frequency as a fraction of thereference clock frequency signal f_(c). The output of the load register4202 is provided to the parallel delta phase register 4204 with a tuningword M.

The DDS circuit 4200 includes a sample clock that generates the clockfrequency f_(c), the phase accumulator 4206, and the lookup table 4210(e.g., phase to amplitude converter). The content of the phaseaccumulator 4206 is updated once per clock cycle f_(c). When time thephase accumulator 4206 is updated, the digital number, M, stored in theparallel delta phase register 4204 is added to the number in the phaseregister 4208 by the adder circuit 4216. Assuming that the number in theparallel delta phase register 4204 is 00 . . . 01 and that the initialcontents of the phase accumulator 4206 is 00 . . . 00. The phaseaccumulator 4206 is updated by 00 . . . 01 per clock cycle. If the phaseaccumulator 4206 is 32-bits wide, 232 clock cycles (over 4 billion) arerequired before the phase accumulator 4206 returns to 00 . . . 00, andthe cycle repeats.

A truncated output 4218 of the phase accumulator 4206 is provided to aphase-to amplitude converter lookup table 4210 and the output of thelookup table 4210 is coupled to a DAC circuit 4212. The truncated output4218 of the phase accumulator 4206 serves as the address to a sine (orcosine) lookup table. An address in the lookup table corresponds to aphase point on the sinewave from 0° to 360°. The lookup table 4210contains the corresponding digital amplitude information for onecomplete cycle of a sinewave. The lookup table 4210 therefore maps thephase information from the phase accumulator 4206 into a digitalamplitude word, which in turn drives the DAC circuit 4212. The output ofthe DAC circuit is a first analog signal 4220 and is filtered by afilter 4214. The output of the filter 4214 is a second analog signal4222, which is provided to a power amplifier coupled to the output ofthe generator circuit.

In one aspect, the electrical signal waveform may be digitized into 1024(210) phase points, although the wave shape may be digitized is anysuitable number of 2n phase points ranging from 256 (28) to281,474,976,710,656 (248), where n is a positive integer, as shown inTABLE 1. The electrical signal waveform may be expressed asA_(n)(θ_(n)), where a normalized amplitude A_(n) at a point n isrepresented by a phase angle θ_(n) is referred to as a phase point atpoint n. The number of discrete phase points n determines the tuningresolution of the DDS circuit 4200 (as well as the DDS circuit 4100shown in FIG. 13).

TABLE 1 specifies the electrical signal waveform digitized into a numberof phase points.

TABLE 1 N Number of Phase Points 2^(n)  8 256 10 1,024 12 4,096 1416,384 16 65,536 18 262,144 20 1,048,576 22 4,194,304 24 16,777,216 2667,108,864 28 268,435,456 . . . . . . 32 4,294,967,296 . . . . . . 48281,474,976,710,656 . . . . . .

The generator circuit algorithms and digital control circuits scan theaddresses in the lookup table 4210, which in turn provides varyingdigital input values to the DAC circuit 4212 that feeds the filter 4214and the power amplifier. The addresses may be scanned according to afrequency of interest. Using the lookup table enables generating varioustypes of shapes that can be converted into an analog output signal bythe DAC circuit 4212, filtered by the filter 4214, amplified by thepower amplifier coupled to the output of the generator circuit, and fedto the tissue in the form of RF energy or fed to an ultrasonictransducer and applied to the tissue in the form of ultrasonicvibrations which deliver energy to the tissue in the form of heat. Theoutput of the amplifier can be applied to an RF electrode, multiple RFelectrodes simultaneously, an ultrasonic transducer, multiple ultrasonictransducers simultaneously, or a combination of RF and ultrasonictransducers, for example. Furthermore, multiple wave shape tables can becreated, stored, and applied to tissue from a generator circuit.

With reference back to FIG. 13, for n=32, and M=1, the phase accumulator4206 steps through 232 possible outputs before it overflows andrestarts. The corresponding output wave frequency is equal to the inputclock frequency divided by 232. If M=2, then the phase register 1708“rolls over” twice as fast, and the output frequency is doubled. Thiscan be generalized as follows.

For a phase accumulator 4206 configured to accumulate n-bits (ngenerally ranges from 24 to 32 in most DDS systems, but as previouslydiscussed n may be selected from a wide range of options), there are 2″possible phase points. The digital word in the delta phase register, M,represents the amount the phase accumulator is incremented per clockcycle. If f_(c) is the clock frequency, then the frequency of the outputsinewave is equal to:

$f_{0} = \frac{M \cdot f_{c}}{2^{n}}$

The above equation is known as the DDS “tuning equation.” Note that thefrequency resolution of the system is equal to

$\frac{f_{o}}{2^{n}}.$For n=32, the resolution is greater than one part in four billion. Inone aspect of the DDS circuit 4200, not all of the bits out of the phaseaccumulator 4206 are passed on to the lookup table 4210, but aretruncated, leaving only the first 13 to 15 most significant bits (MSBs),for example. This reduces the size of the lookup table 4210 and does notaffect the frequency resolution. The phase truncation only adds a smallbut acceptable amount of phase noise to the final output.

The electrical signal waveform may be characterized by a current,voltage, or power at a predetermined frequency. Further, where any oneof the surgical instruments of surgical system 1000 comprises ultrasoniccomponents, the electrical signal waveform may be configured to drive atleast two vibration modes of an ultrasonic transducer of the at leastone surgical instrument. Accordingly, the generator circuit may beconfigured to provide an electrical signal waveform to at least onesurgical instrument wherein the electrical signal waveform ischaracterized by a predetermined wave shape stored in the lookup table4210 (or lookup table 4104 FIG. 13). Further, the electrical signalwaveform may be a combination of two or more wave shapes. The lookuptable 4210 may comprise information associated with a plurality of waveshapes. In one aspect or example, the lookup table 4210 may be generatedby the DDS circuit 4200 and may be referred to as a direct digitalsynthesis table. DDS works by first storing a large repetitive waveformin onboard memory. A cycle of a waveform (sine, triangle, square,arbitrary) can be represented by a predetermined number of phase pointsas shown in TABLE 1 and stored into memory. Once the waveform is storedinto memory, it can be generated at very precise frequencies. The directdigital synthesis table may be stored in a non-volatile memory of thegenerator circuit and/or may be implemented with a FPGA circuit in thegenerator circuit. The lookup table 4210 may be addressed by anysuitable technique that is convenient for categorizing wave shapes.According to one aspect, the lookup table 4210 is addressed according toa frequency of the electrical signal waveform. Additionally, theinformation associated with the plurality of wave shapes may be storedas digital information in a memory or as part of the lookup table 4210.

In one aspect, the generator circuit may be configured to provideelectrical signal waveforms to at least two surgical instrumentssimultaneously. The generator circuit also may be configured to providethe electrical signal waveform, which may be characterized two or morewave shapes, via an output channel of the generator circuit to the twosurgical instruments simultaneously. For example, in one aspect theelectrical signal waveform comprises a first electrical signal to drivean ultrasonic transducer (e.g., ultrasonic drive signal), a second RFdrive signal, and/or a combination thereof. In addition, an electricalsignal waveform may comprise a plurality of ultrasonic drive signals, aplurality of RF drive signals, and/or a combination of a plurality ofultrasonic and RF drive signals.

In addition, a method of operating the generator circuit according tothe present disclosure comprises generating an electrical signalwaveform and providing the generated electrical signal waveform to anyone of the surgical instruments of surgical system 1000, wheregenerating the electrical signal waveform comprises receivinginformation associated with the electrical signal waveform from amemory. The generated electrical signal waveform comprises at least onewave shape. Furthermore, providing the generated electrical signalwaveform to the at least one surgical instrument comprises providing theelectrical signal waveform to at least two surgical instrumentssimultaneously.

The generator circuit as described herein may allow for the generationof various types of direct digital synthesis tables. Examples of waveshapes for RF/Electrosurgery signals suitable for treating a variety oftissue generated by the generator circuit include RF signals with a highcrest factor (which may be used for surface coagulation in RF mode), alow crest factor RF signals (which may be used for deeper tissuepenetration), and waveforms that promote efficient touch-up coagulation.The generator circuit also may generate multiple wave shapes employing adirect digital synthesis lookup table 4210 and, on the fly, can switchbetween particular wave shapes based on the desired tissue effect.Switching may be based on tissue impedance and/or other factors.

In addition to traditional sine/cosine wave shapes, the generatorcircuit may be configured to generate wave shape(s) that maximize thepower into tissue per cycle (i.e., trapezoidal or square wave). Thegenerator circuit may provide wave shape(s) that are synchronized tomaximize the power delivered to the load when driving RF and ultrasonicsignals simultaneously and to maintain ultrasonic frequency lock,provided that the generator circuit includes a circuit topology thatenables simultaneously driving RF and ultrasonic signals. Further,custom wave shapes specific to instruments and their tissue effects canbe stored in a non-volatile memory (NVM) or an instrument EEPROM and canbe fetched upon connecting any one of the surgical instruments ofsurgical system 1000 to the generator circuit.

The DDS circuit 4200 may comprise multiple lookup tables 4104 where thelookup table 4210 stores a waveform represented by a predeterminednumber of phase points (also may be referred to as samples), wherein thephase points define a predetermined shape of the waveform. Thus multiplewaveforms having a unique shape can be stored in multiple lookup tables4210 to provide different tissue treatments based on instrument settingsor tissue feedback. Examples of waveforms include high crest factor RFelectrical signal waveforms for surface tissue coagulation, low crestfactor RF electrical signal waveform for deeper tissue penetration, andelectrical signal waveforms that promote efficient touch-up coagulation.In one aspect, the DDS circuit 4200 can create multiple wave shapelookup tables 4210 and during a tissue treatment procedure (e.g.,“on-the-fly” or in virtual real time based on user or sensor inputs)switch between different wave shapes stored in different lookup tables4210 based on the tissue effect desired and/or tissue feedback.

Accordingly, switching between wave shapes can be based on tissueimpedance and other factors, for example. In other aspects, the lookuptables 4210 can store electrical signal waveforms shaped to maximize thepower delivered into the tissue per cycle (i.e., trapezoidal or squarewave). In other aspects, the lookup tables 4210 can store wave shapessynchronized in such way that they make maximizing power delivery by anyone of the surgical instruments of surgical system 1000 when deliveringRF and ultrasonic drive signals. In yet other aspects, the lookup tables4210 can store electrical signal waveforms to drive ultrasonic and RFtherapeutic, and/or sub-therapeutic, energy simultaneously whilemaintaining ultrasonic frequency lock. Generally, the output wave shapemay be in the form of a sine wave, cosine wave, pulse wave, square wave,and the like. Nevertheless, the more complex and custom wave shapesspecific to different instruments and their tissue effects can be storedin the non-volatile memory of the generator circuit or in thenon-volatile memory (e.g., EEPROM) of the surgical instrument and befetched upon connecting the surgical instrument to the generatorcircuit. One example of a custom wave shape is an exponentially dampedsinusoid as used in many high crest factor “coagulation” waveforms, asshown in FIG. 15.

FIG. 15 illustrates one cycle of a discrete time digital electricalsignal waveform 4300, in accordance with at least one aspect of thepresent disclosure of an analog waveform 4304 (shown superimposed overthe discrete time digital electrical signal waveform 4300 for comparisonpurposes). The horizontal axis represents Time (t) and the vertical axisrepresents digital phase points. The digital electrical signal waveform4300 is a digital discrete time version of the desired analog waveform4304, for example. The digital electrical signal waveform 4300 isgenerated by storing an amplitude phase point 4302 that represents theamplitude per clock cycle T_(clk) over one cycle or period T_(o). Thedigital electrical signal waveform 4300 is generated over one periodT_(o) by any suitable digital processing circuit. The amplitude phasepoints are digital words stored in a memory circuit. In the exampleillustrated in FIGS. 13, 14, the digital word is a six-bit word that iscapable of storing the amplitude phase points with a resolution of 26 or64 bits. It will be appreciated that the examples shown in FIGS. 13, 14is for illustrative purposes and in actual implementations theresolution can be much higher. The digital amplitude phase points 4302over one cycle T_(o) are stored in the memory as a string of stringwords in a lookup table 4104, 4210 as described in connection with FIGS.13, 14, for example. To generate the analog version of the analogwaveform 4304, the amplitude phase points 4302 are read sequentiallyfrom the memory from 0 to T_(o) per clock cycle T_(clk) and areconverted by a DAC circuit 4108, 4212, also described in connection withFIGS. 13, 14. Additional cycles can be generated by repeatedly readingthe amplitude phase points 4302 of the digital electrical signalwaveform 4300 the from 0 to T_(o) for as many cycles or periods as maybe desired. The smooth analog version of the analog waveform 4304 isachieved by filtering the output of the DAC circuit 4108, 4212 by afilter 4112, 4214 (FIGS. 13 and 14). The filtered analog output signal4114, 4222 (FIGS. 13 and 14) is applied to the input of a poweramplifier.

FIG. 16 is a diagram of a control system 12950 configured to provideprogressive closure of a closure member (e.g., closure tube) when thedisplacement member advances distally and couples into a clamp arm(e.g., anvil) to lower the closure force load on the closure member at adesired rate and decrease the firing force load on the firing memberaccording to one aspect of this disclosure. In one aspect, the controlsystem 12950 may be implemented as a nested PID feedback controller. APID controller is a control loop feedback mechanism (controller) tocontinuously calculate an error value as the difference between adesired set point and a measured process variable and applies acorrection based on proportional, integral, and derivative terms(sometimes denoted P, I, and D respectively). The nested PID controllerfeedback control system 12950 includes a primary controller 12952, in aprimary (outer) feedback loop 12954 and a secondary controller 12955 ina secondary (inner) feedback loop 12956. The primary controller 12952may be a PID controller 12972 as shown in FIG. 17, and the secondarycontroller 12955 also may be a PID controller 12972 as shown in FIG. 17.The primary controller 12952 controls a primary process 12958 and thesecondary controller 12955 controls a secondary process 12960. Theoutput 12966 of the primary process 12958 is subtracted from a primaryset point SP₁ by a first summer 12962. The first summer 12962 produces asingle sum output signal which is applied to the primary controller12952. The output of the primary controller 12952 is the secondary setpoint SP₂. The output 12968 of the secondary process 12960 is subtractedfrom the secondary set point SP₂ by a second summer 12964.

In the context of controlling the displacement of a closure tube, thecontrol system 12950 may be configured such that the primary set pointSP₁ is a desired closure force value and the primary controller 12952 isconfigured to receive the closure force from a torque sensor coupled tothe output of a closure motor and determine a set point SP₂ motorvelocity for the closure motor. In other aspects, the closure force maybe measured with strain gauges, load cells, or other suitable forcesensors. The closure motor velocity set point SP₂ is compared to theactual velocity of the closure tube, which is determined by thesecondary controller 12955. The actual velocity of the closure tube maybe measured by comparing measuring the displacement of the closure tubewith the position sensor and measuring elapsed time with atimer/counter. Other techniques, such as linear or rotary encoders maybe employed to measure displacement of the closure tube. The output12968 of the secondary process 12960 is the actual velocity of theclosure tube. This closure tube velocity output 12968 is provided to theprimary process 12958 which determines the force acting on the closuretube and is fed back to the adder 12962, which subtracts the measuredclosure force from the primary set point SP₁. The primary set point SP₁may be an upper threshold or a lower threshold. Based on the output ofthe adder 12962, the primary controller 12952 controls the velocity anddirection of the closure motor. The secondary controller 12955 controlsthe velocity of the closure motor based on the actual velocity ofclosure tube measured by the secondary process 12960 and the secondaryset point SP₂, which is based on a comparison of the actual firing forceand the firing force upper and lower thresholds.

FIG. 17 illustrates a PID feedback control system 12970 according to oneaspect of this disclosure. The primary controller 12952 or the secondarycontroller 12955, or both, may be implemented as a PID controller 12972.In one aspect, the PID controller 12972 may comprise a proportionalelement 12974 (P), an integral element 12976 (I), and a derivativeelement 12978 (D). The outputs of the P, I, D elements 12974, 12976,12978 are summed by a summer 12986, which provides the control variableμ(t) to the process 12980. The output of the process 12980 is theprocess variable y(t). A summer 12984 calculates the difference betweena desired set point r(t) and a measured process variable y(t), receivedby feedback loop 12982. The PID controller 12972 continuously calculatesan error value e(t) (e.g., difference between closure force thresholdand measured closure force) as the difference between a desired setpoint r(t) (e.g., closure force threshold) and a measured processvariable y(t) (e.g., velocity and direction of closure tube) and appliesa correction based on the proportional, integral, and derivative termscalculated by the proportional element 12974 (P), integral element 12976(I), and derivative element 12978 (D), respectively. The PID controller12972 attempts to minimize the error e(t) over time by adjustment of thecontrol variable μ(t) (e.g., velocity and direction of the closuretube).

In accordance with the PID algorithm, the “P” element 12974 accounts forpresent values of the error. For example, if the error is large andpositive, the control output will also be large and positive. Inaccordance with the present disclosure, the error term e(t) is thedifferent between the desired closure force and the measured closureforce of the closure tube. The “I” element 12976 accounts for pastvalues of the error. For example, if the current output is notsufficiently strong, the integral of the error will accumulate overtime, and the controller will respond by applying a stronger action. The“D” element 12978 accounts for possible future trends of the error,based on its current rate of change. For example, continuing the Pexample above, when the large positive control output succeeds inbringing the error closer to zero, it also puts the process on a path tolarge negative error in the near future. In this case, the derivativeturns negative and the D module reduces the strength of the action toprevent this overshoot.

It will be appreciated that other variables and set points may bemonitored and controlled in accordance with the feedback control systems12950, 12970. For example, the adaptive closure member velocity controlalgorithm described herein may measure at least two of the followingparameters: firing member stroke location, firing member load,displacement of cutting element, velocity of cutting element, closuretube stroke location, closure tube load, among others.

Various aspects are directed to improved ultrasonic surgical devices,electrosurgical devices and generators for use therewith. Aspects of theultrasonic surgical devices can be configured for transecting and/orcoagulating tissue during surgical procedures, for example. Aspects ofthe electrosurgical devices can be configured for transecting,coagulating, scaling, welding and/or desiccating tissue during surgicalprocedures, for example.

Aspects of the generator utilize high-speed analog-to-digital sampling(e.g., approximately 200× oversampling, depending on frequency) of thegenerator drive signal current and voltage, along with digital signalprocessing, to provide a number of advantages and benefits over knowngenerator architectures. In one aspect, for example, based on currentand voltage feedback data, a value of the ultrasonic transducer staticcapacitance, and a value of the drive signal frequency, the generatormay determine the motional branch current of an ultrasonic transducer.This provides the benefit of a virtually tuned system, and simulates thepresence of a system that is tuned or resonant with any value of thestatic capacitance (e.g., C0 in FIG. 6) at any frequency. Accordingly,control of the motional branch current may be realized by tuning out theeffects of the static capacitance without the need for a tuninginductor. Additionally, the elimination of the tuning inductor may notdegrade the generator's frequency lock capabilities, as frequency lockcan be realized by suitably processing the current and voltage feedbackdata.

High-speed analog-to-digital sampling of the generator drive signalcurrent and voltage, along with digital signal processing, may alsoenable precise digital filtering of the samples. For example, aspects ofthe generator may utilize a low-pass digital filter (e.g., a finiteimpulse response (FIR) filter) that rolls off between a fundamentaldrive signal frequency and a second-order harmonic to reduce theasymmetrical harmonic distortion and EMI-induced noise in current andvoltage feedback samples. The filtered current and voltage feedbacksamples represent substantially the fundamental drive signal frequency,thus enabling a more accurate impedance phase measurement with respectto the fundamental drive signal frequency and an improvement in thegenerator's ability to maintain resonant frequency lock. The accuracy ofthe impedance phase measurement may be further enhanced by averagingfalling edge and rising edge phase measurements, and by regulating themeasured impedance phase to 0°.

Various aspects of the generator may also utilize the high-speedanalog-to-digital sampling of the generator drive signal current andvoltage, along with digital signal processing, to determine real powerconsumption and other quantities with a high degree of precision. Thismay allow the generator to implement a number of useful algorithms, suchas, for example, controlling the amount of power delivered to tissue asthe impedance of the tissue changes and controlling the power deliveryto maintain a constant rate of tissue impedance increase. Some of thesealgorithms are used to determine the phase difference between thegenerator drive signal current and voltage signals. At resonance, thephase difference between the current and voltage signals is zero. Thephase changes as the ultrasonic system goes off-resonance. Variousalgorithms may be employed to detect the phase difference and adjust thedrive frequency until the ultrasonic system returns to resonance, i.e.,the phase difference between the current and voltage signals goes tozero. The phase information also may be used to infer the conditions ofthe ultrasonic blade. As discussed with particularity below, the phasechanges as a function of the temperature of the ultrasonic blade.Therefore, the phase information may be employed to control thetemperature of the ultrasonic blade. This may be done, for example, byreducing the power delivered to the ultrasonic blade when the ultrasonicblade runs too hot and increasing the power delivered to the ultrasonicblade when the ultrasonic blade runs too cold.

Various aspects of the generator may have a wide frequency range andincreased output power necessary to drive both ultrasonic surgicaldevices and electrosurgical devices. The lower voltage, higher currentdemand of electrosurgical devices may be met by a dedicated tap on awideband power transformer, thereby eliminating the need for a separatepower amplifier and output transformer. Moreover, sensing and feedbackcircuits of the generator may support a large dynamic range thataddresses the needs of both ultrasonic and electrosurgical applicationswith minimal distortion.

Various aspects may provide a simple, economical means for the generatorto read from, and optionally write to, a data circuit (e.g., asingle-wire bus device, such as a one-wire protocol EEPROM known underthe trade name “1-Wire”) disposed in an instrument attached to thehandpiece using existing multi-conductor generator/handpiece cables. Inthis way, the generator is able to retrieve and processinstrument-specific data from an instrument attached to the handpiece.This may enable the generator to provide better control and improveddiagnostics and error detection. Additionally, the ability of thegenerator to write data to the instrument makes possible newfunctionality in terms of, for example, tracking instrument usage andcapturing operational data. Moreover, the use of frequency band permitsthe backward compatibility of instruments containing a bus device withexisting generators.

Disclosed aspects of the generator provide active cancellation ofleakage current caused by unintended capacitive coupling betweennon-isolated and patient-isolated circuits of the generator. In additionto reducing patient risk, the reduction of leakage current may alsolessen electromagnetic emissions. These and other benefits of aspects ofthe present disclosure will be apparent from the description to follow.

It will be appreciated that the terms “proximal” and “distal” are usedherein with reference to a clinician gripping a handpiece. Thus, an endeffector is distal with respect to the more proximal handpiece. It willbe further appreciated that, for convenience and clarity, spatial termssuch as “top” and “bottom” may also be used herein with respect to theclinician gripping the handpiece. However, surgical devices are used inmany orientations and positions, and these terms are not intended to belimiting and absolute.

FIG. 18 is an alternative system 132000 for controlling the frequency ofan ultrasonic electromechanical system 132002 and detecting theimpedance thereof, in accordance with at least one aspect of the presentdisclosure. The system 132000 may be incorporated into a generator. Aprocessor 132004 coupled to a memory 132026 programs a programmablecounter 132006 to tune to the output frequency f_(o) of the ultrasonicelectromechanical system 132002. The input frequency is generated by acrystal oscillator 132008 and is input into a fixed counter 132010 toscale the frequency to a suitable value. The outputs of the fixedcounter 132010 and the programmable counter 132006 are applied to aphase/frequency detector 132012. The output of the phase/frequencydetector 132012 is applied to an amplifier/active filter circuit 132014to generate a tuning voltage V_(t) that is applied to a voltagecontrolled oscillator 132016 (VCO). The VCO 132016 applies the outputfrequency f_(o) to an ultrasonic transducer portion of the ultrasonicelectromechanical system 132002, shown here modeled as an equivalentelectrical circuit. The voltage and current signals applied to theultrasonic transducer are monitored by a voltage sensor 132018 and acurrent sensor 132020.

The outputs of the voltage and current sensors 132018,132020 are appliedto another phase/frequency detector 132022 to determine the phase anglebetween the voltage and current as measured by the voltage and currentsensors 132018, 132020. The output of the phase/frequency detector132022 is applied to one channel of a high speed analog to digitalconverter 132024 (ADC) and is provided to the processor 132004therethrough. Optionally, the outputs of the voltage and current sensors132018, 132020 may be applied to respective channels of the two-channelADC 132024 and provided to the processor 132004 for zero crossing, FFT,or other algorithm described herein for determining the phase anglebetween the voltage and current signals applied to the ultrasonicelectromechanical system 132002.

Optionally the tuning voltage V_(t), which is proportional to the outputfrequency f_(o), may be fed back to the processor 132004 via the ADC132024. This provides the processor 132004 with a feedback signalproportional to the output frequency f_(o) and can use this feedback toadjust and control the output frequency f_(o).

Temperature Inference

FIGS. 19A-19B are graphical representations 133000, 133010 of compleximpedance spectra of the same ultrasonic device with a cold (roomtemperature) and hot ultrasonic blade, in accordance with at least oneaspect of the present disclosure. As used herein, a cold ultrasonicblade 133002, 133012 refers to an ultrasonic blade at room temperatureand a hot ultrasonic blade 133004, 133014 refers to an ultrasonic bladeafter it is frictionally heated in use. FIG. 19A is a graphicalrepresentation 133000 of impedance phase angle φ as a function ofresonant frequency f_(o) of the same ultrasonic device with a cold andhot ultrasonic blade and FIG. 19B is a graphical representation 133010of impedance magnitude |Z| as a function of resonant frequency f_(o) ofthe same ultrasonic device with a cold and hot ultrasonic blade. Theimpedance phase angle φ and impedance magnitude |Z| are at a minimum atthe resonant frequency f₀.

The ultrasonic transducer impedance Z_(g)(t) can be measured as theratio of the drive signal generator voltage V_(g)(t) and currentI_(g)(t) drive signals:

${Z_{g}(t)} = \frac{V_{g}(t)}{I_{g}(t)}$

As shown in FIG. 19A, when the ultrasonic blade is cold, e.g., at roomtemperature and not frictionally heated, the electromechanical resonantfrequency f_(o) of the ultrasonic device is approximately 55,500 Hz andthe excitation frequency of the ultrasonic transducer is set to 55,500Hz. Thus, when the ultrasonic transducer is excited at theelectromechanical resonant frequency f_(o) and the ultrasonic blade iscold the phase angle φ is at minimum or approximately 0 Rad as indicatedby the cold blade plot 133002. As shown in FIG. 19B, when the ultrasonicblade is cold and the ultrasonic transducer is excited at theelectromechanical resonant frequency f₀, the impedance magnitude |Z| is800Ω, e.g., the impedance magnitude |Z| is at a minimum impedance, andthe drive signal amplitude is at a maximum due to the series resonanceequivalent circuit of the ultrasonic electromechanical system asdepicted in FIG. 6.

With reference now back to FIGS. 19A and 19B, when the ultrasonictransducer is driven by generator voltage V_(g)(t) and generator currentI_(g)(t) signals at the electromechanical resonant frequency f_(o) of55,500 Hz, the phase angle φ between the generator voltage V_(g)(t) andgenerator current I_(g)(t) signals is zero, the impedance magnitude |Z|is at a minimum impedance, e.g., 800Ω, and the signal amplitude is at apeak or maximum due to the series resonance equivalent circuit of theultrasonic electromechanical system. As the temperature of theultrasonic blade increases, due to frictional heat generated in use, theelectromechanical resonant frequency f₀′ of the ultrasonic devicedecreases. Since the ultrasonic transducer is still driven by generatorvoltage V_(g)(t) and generator current I_(g)(t) signals at the previous(cold blade) electromechanical resonant frequency f_(o) of 55,500 Hz,the ultrasonic device operates off-resonance f₀′ causing a shift in thephase angle φ between the generator voltage V_(g)(t) and generatorcurrent I_(g)(t) signals. There is also an increase in impedancemagnitude |Z| and a drop in peak magnitude of the drive signal relativeto the previous (cold blade) electromechanical resonant frequency of55,500 Hz. Accordingly, the temperature of the ultrasonic blade may beinferred by measuring the phase angle φ between the generator voltageV_(g)(t) and the generator current I_(g)(t) signals as theelectromechanical resonant frequency f_(o) changes due to the changes intemperature of the ultrasonic blade.

As previously described, an electromechanical ultrasonic system includesan ultrasonic transducer, a waveguide, and an ultrasonic blade. Aspreviously discussed, the ultrasonic transducer may be modeled as anequivalent series resonant circuit (see FIG. 6) comprising first branchhaving a static capacitance and a second “motional” branch having aserially connected inductance, resistance and capacitance that definethe electromechanical properties of a resonator. The electromechanicalultrasonic system has an initial electromechanical resonant frequencydefined by the physical properties of the ultrasonic transducer, thewaveguide, and the ultrasonic blade. The ultrasonic transducer isexcited by an alternating voltage V_(g)(t) and current I_(g)(t) signalat a frequency equal to the electromechanical resonant frequency, e.g.,the resonant frequency of the electromechanical ultrasonic system. Whenthe electromechanical ultrasonic system is excited at the resonantfrequency, the phase angle φ between the voltage V_(g)(t) and currentI_(g)(t) signals is zero.

Stated in another way, at resonance, the analogous inductive impedanceof the electromechanical ultrasonic system is equal to the analogouscapacitive impedance of the electromechanical ultrasonic system. As theultrasonic blade heats up, for example due to frictional engagement withtissue, the compliance of the ultrasonic blade (modeled as an analogouscapacitance) causes the resonant frequency of the electromechanicalultrasonic system to shift. In the present example, the resonantfrequency of the electromechanical ultrasonic system decreases as thetemperature of the ultrasonic blade increases. Thus, the analogousinductive impedance of the electromechanical ultrasonic system is nolonger equal to the analogous capacitive impedance of theelectromechanical ultrasonic system causing a mismatch between the drivefrequency and the new resonant frequency of the electromechanicalultrasonic system. Thus, with a hot ultrasonic blade, theelectromechanical ultrasonic system operates “off-resonance.” Themismatch between the drive frequency and the resonant frequency ismanifested as a phase angle φ between the voltage V_(g)(t) and currentI_(g)(t) signals applied to the ultrasonic transducer.

As previously discussed, the generator electronics can easily monitorthe phase angle φ between the voltage V_(g)(t) and current I_(g)(t)signals applied to the ultrasonic transducer. The phase angle φ may bedetermined through Fourier analysis, weighted least-squares estimation,Kalman filtering, space-vector-based techniques, zero-crossing method,Lissajous figures, three-voltmeter method, crossed-coil method, vectorvoltmeter and vector impedance methods, phase standard instruments,phase-locked loops, among other techniques previously described. Thegenerator can continuously monitor the phase angle φ and adjust thedrive frequency until the phase angle φ goes to zero. At this point, thenew drive frequency is equal to the new resonant frequency of theelectromechanical ultrasonic system. The change in phase angle φ and/orgenerator drive frequency can be used as an indirect or inferredmeasurement of the temperature of the ultrasonic blade.

A variety of techniques are available to estimate temperature from thedata in these spectra. Most notably, a time variant, non-linear set ofstate space equations can be employed to model the dynamic relationshipbetween the temperature of the ultrasonic blade and the measuredimpedance:

${Z_{g}(t)} = \frac{V_{g}(t)}{I_{g}(t)}$across a range of generator drive frequencies, where the range ofgenerator drive frequencies is specific to device model.

Methods of Temperature Estimation

One aspect of estimating or inferring the temperature of an ultrasonicblade may include three steps. First, define a state space model oftemperature and frequency that is time and energy dependent. To modeltemperature as a function of frequency content, a set of non-linearstate space equations are used to model the relationship between theelectromechanical resonant frequency and the temperature of theultrasonic blade. Second, apply a Kalman filter to improve the accuracyof the temperature estimator and state space model over time. Third, astate estimator is provided in the feedback loop of the Kalman filter tocontrol the power applied to the ultrasonic transducer, and hence theultrasonic blade, to regulate the temperature of the ultrasonic blade.The three steps are described hereinbelow.

Step 1

The first step is to define a state space model of temperature andfrequency that is time and energy dependent. To model temperature as afunction of frequency content, a set of non-linear state space equationsare used to model the relationship between the electromechanicalresonant frequency and the temperature of the ultrasonic blade. In oneaspect, the state space model is defined by:

$\begin{bmatrix}{\overset{.}{F}}_{n} \\\overset{.}{T}\end{bmatrix} = {f\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$$\overset{.}{y} = {h\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$

The state space model represents the rate of change of the naturalfrequency of the electromechanical ultrasonic system {dot over (F)}_(n)and the rate of change of the temperature {dot over (T)} of theultrasonic blade with respect to natural frequency F_(n)(t), temperatureT(t), energy E(t), and time t. {dot over (y)} represents theobservability of variables that are measurable and observable such asthe natural frequency F_(n)(t) of the electromechanical ultrasonicsystem, the temperature T(t) of the ultrasonic blade, the energy E(t)applied to the ultrasonic blade, and time t. The temperature T(t) of theultrasonic blade is observable as an estimate.

Step 2

The second step is to apply a Kalman filter to improve temperatureestimator and state space model. FIG. 20 is a diagram of a Kalman filter133020 to improve the temperature estimator and state space model basedon impedance according to the equation:

${Z_{g}(t)} = \frac{V_{g}(t)}{I_{g}(t)}$which represents the impedance across an ultrasonic transducer measuredat a variety of frequencies, in accordance with at least one aspect ofthe present disclosure.

The Kalman filter 133020 may be employed to improve the performance ofthe temperature estimate and allows for the augmentation of externalsensors, models, or prior information to improve temperature predictionin the midst of noisy data. The Kalman filter 133020 includes aregulator 133022 and a plant 133024. In control theory a plant 133024 isthe combination of process and actuator. A plant 133024 may be referredto with a transfer function which indicates the relation between aninput signal and the output signal of a system. The regulator 133022includes a state estimator 133026 and a controller K 133028. The stateregulator 133026 includes a feedback loop 133030. The state regulator133026 receives y, the output of the plant 133024, as an input and afeedback variable u. The state estimator 133026 is an internal feedbacksystem that converges to the true value of the state of the system. Theoutput of the state estimator 133026 is {circumflex over (x)}, the fullfeedback control variable including F_(n)(t) of the electromechanicalultrasonic system, the estimate of the temperature T(t) of theultrasonic blade, the energy E(t) applied to the ultrasonic blade, thephase angle φ, and time t. The input into the controller K 133028 is{circumflex over (x)} and the output of the controller K 133028 u is fedback to the state estimator 133026 and t of the plant 133024.

Kalman filtering, also known as linear quadratic estimation (LQE), is analgorithm that uses a series of measurements observed over time,containing statistical noise and other inaccuracies, and producesestimates of unknown variables that tend to be more accurate than thosebased on a single measurement alone, by estimating a joint probabilitydistribution over the variables for each timeframe and thus calculatingthe maximum likelihood estimate of actual measurements. The algorithmworks in a two-step process. In a prediction step, the Kalman filter133020 produces estimates of the current state variables, along withtheir uncertainties. Once the outcome of the next measurement(necessarily corrupted with some amount of error, including randomnoise) is observed, these estimates are updated using a weightedaverage, with more weight being given to estimates with highercertainty. The algorithm is recursive and can run in real time, usingonly the present input measurements and the previously calculated stateand its uncertainty matrix; no additional past information is required.

The Kalman filter 133020 uses a dynamics model of the electromechanicalultrasonic system, known control inputs to that system, and multiplesequential measurements (observations) of the natural frequency andphase angle of the applied signals (e.g., magnitude and phase of theelectrical impedance of the ultrasonic transducer) to the ultrasonictransducer to form an estimate of the varying quantities of theelectromechanical ultrasonic system (its state) to predict thetemperature of the ultrasonic blade portion of the electromechanicalultrasonic system that is better than an estimate obtained using onlyone measurement alone. As such, the Kalman filter 133020 is an algorithmthat includes sensor and data fusion to provide the maximum likelihoodestimate of the temperature of the ultrasonic blade.

The Kalman filter 133020 deals effectively with uncertainty due to noisymeasurements of the applied signals to the ultrasonic transducer tomeasure the natural frequency and phase shift data and also dealseffectively with uncertainty due to random external factors. The Kalmanfilter 133020 produces an estimate of the state of the electromechanicalultrasonic system as an average of the predicted state of the system andof the new measurement using a weighted average. Weighted values providebetter (i.e., smaller) estimated uncertainty and are more “trustworthy”than unweighted values The weights may be calculated from thecovariance, a measure of the estimated uncertainty of the prediction ofthe system's state. The result of the weighted average is a new stateestimate that lies between the predicted and measured state, and has abetter estimated uncertainty than either alone. This process is repeatedat every time step, with the new estimate and its covariance informingthe prediction used in the following iteration. This recursive nature ofthe Kalman filter 133020 requires only the last “best guess,” ratherthan the entire history, of the state of the electromechanicalultrasonic system to calculate a new state.

The relative certainty of the measurements and current state estimate isan important consideration, and it is common to discuss the response ofthe filter in terms of the gain K of the Kalman filter 133020. TheKalman gain K is the relative weight given to the measurements andcurrent state estimate, and can be “tuned” to achieve particularperformance. With a high gain K, the Kalman filter 133020 places moreweight on the most recent measurements, and thus follows them moreresponsively. With a low gain K, the Kalman filter 133020 follows themodel predictions more closely. At the extremes, a high gain close toone will result in a more jumpy estimated trajectory, while low gainclose to zero will smooth out noise but decrease the responsiveness.

When performing the actual calculations for the Kalman filter 133020 (asdiscussed below), the state estimate and covariances are coded intomatrices to handle the multiple dimensions involved in a single set ofcalculations. This allows for a representation of linear relationshipsbetween different state variables (such as position, velocity, andacceleration) in any of the transition models or covariances. Using aKalman filter 133020 does not assume that the errors are Gaussian.However, the Kalman filter 133020 yields the exact conditionalprobability estimate in the special case that all errors areGaussian-distributed.

Step 3

The third step uses a state estimator 133026 in the feedback loop 133032of the Kalman filter 133020 for control of power applied to theultrasonic transducer, and hence the ultrasonic blade, to regulate thetemperature of the ultrasonic blade.

FIG. 21 is a graphical depiction 133040 of three probabilitydistributions employed by the state estimator 133026 of the Kalmanfilter 133020 shown in FIG. 20 to maximize estimates, in accordance withat least one aspect of the present disclosure. The probabilitydistributions include the prior probability distribution 133042, theprediction (state) probability distribution 133044, and the observationprobability distribution 133046. The three probability distributions133042, 133044, 133046 are used in feedback control of power applied toan ultrasonic transducer to regulate temperature based on impedanceacross the ultrasonic transducer measured at a variety of frequencies,in accordance with at least one aspect of the present disclosure. Theestimator used in feedback control of power applied to an ultrasonictransducer to regulate temperature based on impedance is defined by theexpression:

${Z_{g}(t)} = \frac{V_{g}(t)}{I_{g}(t)}$which is the impedance across the ultrasonic transducer measured at avariety of frequencies, in accordance with at least one aspect of thepresent disclosure.

The prior probability distribution 133042 includes a state variancedefined by the expression:(σ_(k) ⁻)²=σ_(k-1) ²+σ_(P) _(k) ²The state variance (σ_(k) ⁻) is used to predict the next state of thesystem, which is represented as the prediction (state) probabilitydistribution 133044. The observation probability distribution 133046 isthe probability distribution of the actual observation of the state ofthe system where the observation variance σ_(m) is used to define thegain, which is defined by the following expression:

$K = \frac{\left( \sigma_{k}^{-} \right)^{2}}{\left( \sigma_{k}^{-} \right)^{2} + \sigma_{m}^{2}}$

Feedback Control

Power input is decreased to ensure that the temperature (as estimated bythe state estimator and of the Kalman filter) is controlled.

In one aspect, the initial proof of concept assumed a static, linearrelationship between the natural frequency of the electromechanicalultrasonic system and the temperature of the ultrasonic blade. Byreducing the power as a function of the natural frequency of theelectromechanical ultrasonic system (i.e., regulating temperature withfeedback control), the temperature of the ultrasonic blade tip could becontrolled directly. In this example, the temperature of the distal tipof the ultrasonic blade can be controlled to not exceed the meltingpoint of the Teflon pad.

FIG. 22A is a graphical representation 133050 of temperature versus timeof an ultrasonic device without temperature feedback control.Temperature (° C.) of the ultrasonic blade is shown along the verticalaxis and time (sec) is shown along the horizontal axis. The test wasconducted with a chamois located in the jaws of the ultrasonic device.One jaw is the ultrasonic blade and the other jaw is the clamp arm witha TEFLON pad. The ultrasonic blade was excited at the resonant frequencywhile in frictional engagement with the chamois clamped between theultrasonic blade and the clamp arm. Over time, the temperature (° C.) ofthe ultrasonic blade increases due to the frictional engagement with thechamois. Over time, the temperature profile 133052 of the ultrasonicblade increases until the chamois sample is cut after about 19.5 secondsat a temperature of 220° C. as indicated at point 133054. Withouttemperature feedback control, after cutting the chamois sample, thetemperature of the ultrasonic blade increases to a temperature wellabove the melting point of TEFLON ˜380° C. up to ˜490° C. At point133056 the temperature of the ultrasonic blade reaches a maximumtemperature of 490° C. until the TEFLON pad is completely melted. Thetemperature of the ultrasonic blade drops slightly from the peaktemperature at point 133056 after the pad is completely gone.

FIG. 22B is a plot of temperature versus time of an ultrasonic devicewith temperature feedback control, in accordance with at least oneaspect of the present disclosure. Temperature (° C.) of the ultrasonicblade is shown along the vertical axis and the time (sec) is shown alongthe horizontal axis. The test was conducted with a chamois samplelocated in the jaws of the ultrasonic device. One jaw is the ultrasonicblade and the other jaw is the clamp arm with a TEFLON pad. Theultrasonic blade was excited at the resonant frequency while infrictional engagement with the chamois clamped between the ultrasonicblade and the clamp arm pad. Over time, the temperature profile 133062of the ultrasonic blade increases until the chamois sample is cut afterabout 23 seconds at a temperature of 220° C. as indicated at point133064. With temperature feedback control, the temperature of theultrasonic blade increases up to a maximum temperature of about 380° C.,just below the melting point of TEFLON, as indicated at point 133066 andthen is lowered to an average of about 330° C. as indicated generally atregion 133068, thus preventing the TEFLON pad from melting.

Controlled Thermal Management (CTM) for Pad Protection

In one aspect, the present disclosure provides a controlled thermalmanagement (CTM) algorithm to regulate temperature with feedbackcontrol. The output of the feedback control can be used to prevent theultrasonic end effector clamp arm pad from burning through, which is nota desirable effect for ultrasonic surgical instruments. As previouslydiscussed, in general, pad burn through is caused by the continuedapplication of ultrasonic energy to an ultrasonic blade in contact withthe pad after tissue grasped in the end effector has been transected.

The CTM algorithm leverages the fact that the resonant frequency of anultrasonic blade, general made of titanium, varies in proportion totemperature. As the temperature increases, the modulus of elasticity ofthe ultrasonic blade decreases, and so does the natural frequency of theultrasonic blade. A factor to consider is that when the distal end ofthe ultrasonic blade is hot but the waveguide is cold, there is adifferent frequency difference (delta) to achieve a predeterminedtemperature than when the distal end of the ultrasonic blade and thewaveguide are both hot.

In one aspect, the CTM algorithm calculates a change in frequency of theultrasonic transducer drive signal that is required to reach a certainpredetermined temperature as a function of the resonant frequency of theultrasonic electromechanical system at the beginning of activation (atlock). The ultrasonic electromechanical system comprising an ultrasonictransducer coupled to an ultrasonic blade by an ultrasonic waveguide hasa predefined resonant frequency that varies with temperature. Theresonant frequency of the ultrasonic electromechanical system at lockcan be employed to estimate the change in ultrasonic transducer drivefrequency that is required to achieve a temperature end point to accountfor the initial thermal state of the ultrasonic blade. The resonantfrequency of the ultrasonic electromechanical system can vary as afunction of temperature of the ultrasonic transducer or ultrasonicwaveguide or ultrasonic blade or a combination of these components.

FIG. 23 is a graphical representation 133300 of the relationship betweeninitial resonant frequency (frequency at lock) and the change infrequency (delta frequency) required to achieve a temperature ofapproximately 340° C., in accordance with at least one aspect of thepresent disclosure. The change in frequency required to reach anultrasonic blade temperature of approximately 340° C. is shown along thevertical axis and the resonant frequency of the electromechanicalultrasonic system at lock is shown along the horizontal axis. Based onmeasurement data points 133302 shown as scatter plot there is a linearrelationship 133304 between the change in frequency required to reach anultrasonic blade temperature of approximately 340° C. and the resonantfrequency at lock.

At resonant frequency lock, the CTM algorithm employs the linearrelationship 133304 between the lock frequency and the delta frequencyrequired to achieve a temperature just below the melting point of aTEFLON pad (approximately 340° C.). Once the frequency is within acertain buffer distance from a lower bound on frequency, as shown inFIG. 24, a feedback control system 133310 comprising an ultrasonicgenerator 133312 regulates the electrical current (i) set point appliedto the ultrasonic transducer of the ultrasonic electromechanical system133314 to prevent the frequency (f) of the ultrasonic transducer fromdecreasing lower than a predetermined threshold, in accordance with atleast one aspect of the present disclosure. Decreasing the electricalcurrent set point decreases the displacement of the ultrasonic blade,which in turn decreases the temperature of the ultrasonic blade andincreases the natural frequency of the ultrasonic blade. Thisrelationship allows a change in the electrical current applied to theultrasonic transducer to regulate the natural frequency of theultrasonic blade and indirectly control the temperature of theultrasonic blade or the ultrasonic electromechanical system 133314. Inone aspect, the generator 133312 may be implemented as the ultrasonicgenerator described with reference to FIGS. 2, 7, 8A-8C, and 9A-9B, forexample. The feedback control system 133310 may be implemented as thePID controller described with reference to FIGS. 16-17, for example.

FIG. 25 is a flow diagram 133320 of a process or logic configuration ofa controlled thermal management (CTM) algorithm to protect the clamp armpad in an ultrasonic end effector, in accordance with at least oneaspect of the present disclosure. The process or logic configurationillustrated by way of the flow diagram 133320 may be executed by theultrasonic generator 133312 as described herein or by control circuitslocated in the ultrasonic instrument or a combination thereof. Aspreviously discussed, the generator 133312 may be implemented as thegenerator described with reference to FIGS. 2, 7, 8A-8C, and 9A-9B, forexample.

In one aspect, initially the control circuit in the generator 133312activates 133322 the ultrasonic instrument by applying an electricalcurrent to the ultrasonic transducer. The resonant frequency of theultrasonic electromechanical system is initially locked at initialconditions where the ultrasonic blade temperature is cold or close toroom temperature. As the temperature of the ultrasonic blade increasesdue to frictional contact with tissue, for example, the control circuitmonitors the change or delta in the resonant frequency of the ultrasonicelectromechanical system and determines 133324 whether the deltafrequency threshold for a predetermined blade temperature has beenreached. If the delta frequency is below the threshold, the processcontinues along the NO branch and the control circuit continues to seek133325 the new resonant frequency and monitor the delta frequency. Whenthe delta frequency meets or exceeds the delta frequency threshold, theprocess continues along the YES branch and calculates 133326 a new lowerfrequency limit (threshold), which corresponds to the melting point ofthe clamp arm pad. In one non-limiting example, the clamp arm pad ismade of TEFLON and the melting point is approximately 340° C.

Once a new frequency lower limit is calculated 133326, the controlcircuit determines 133328 if the resonant frequency is near the newlycalculated lower frequency limit. For example, in the case of a TEFLONclamp arm pad, the control circuit determines 133328 if the ultrasonicblade temperature is approaching 350° C., for example, based on thecurrent resonant frequency. If the current resonant frequency is abovethe lower frequency limit, the process continues along the NO branch andapplies 133330 a normal level of electrical current to the ultrasonictransducer suitable for tissue transection. Alternatively, if thecurrent resonant frequency is at or below the lower frequency limit, theprocess continues along the YES branch and regulates 133332 the resonantfrequency by modifying the electrical current applied to the ultrasonictransducer. In ne aspect, the control circuit employs a PID controlleras described with reference to FIGS. 16-17, for example. The controlcircuit regulates 133332 the frequency in a loop to determine 133328when the frequency is near the lower limit until the “seal and cut”surgical procedure is terminated and the ultrasonic transducer isdeactivated. Since the CTM algorithm depicted by the logic flow diagram133320 only has an effect at or near the melting point of the clamp armpad, the CTM algorithm is activated after the tissue is transected.

Burst pressure testing conducted on samples indicates that there is noimpact on the burst pressure of the seal when the CTM process or logicconfiguration depicted by the logic flow diagram 133320 is employed toseal and cut vessels or other tissue. Furthermore, based on testsamples, transection times were affected. Moreover, temperaturemeasurements confirm that the ultrasonic blade temperature is bounded bythe CTM algorithm compared to devices without CTM feedback algorithmcontrol and devices that underwent 10 firings at maximum power for tenseconds against the pad with 5 seconds rest between firings showedsignificantly reduced pad wear whereas no device without CTM algorithmfeedback control lasted more than 2 firings in this abuse test.

FIG. 26 is a graphical representation 133340 of temperature versus timecomparing the desired temperature of an ultrasonic blade with a smartultrasonic blade and a conventional ultrasonic blade, in accordance withat least one aspect of the present disclosure. Temperature (deg. C) isshown along the vertical axis and Time (sec) is shown along thehorizontal axis. In the plot, the dash-dot line is a temperaturethreshold 133342 that represents the desired temperature of theultrasonic blade. The solid line is a temperature versus time curve133344 of a smart ultrasonic blade under the control of the CTMalgorithm described with reference to FIGS. 24 and 25. The dotted lineis a temperature versus time curve 133346 of a regular ultrasonic bladethat is not under the control of the CTM algorithm described withreference to FIGS. 24 and 25. As shown. Once the temperature of thesmart ultrasonic blade under the control of the CTM algorithm exceedsthe desired temperature threshold (˜340° C.), the CTM algorithm takescontrol and regulates the temperature of the smart ultrasonic blade tomatch the threshold as closely as possible until the transectionprocedure is completed and the power to the ultrasonic transducer isdeactivated or cut off.

In another aspect, the present disclosure provides a CTM algorithm for a“seal only” tissue effect by an ultrasonic device, such as ultrasonicshears, for example. Generally speaking, ultrasonic surgical instrumentstypically seal and cut tissue simultaneously. Creating an ultrasonicdevice configured to seal only without cutting has not been difficult toachieve using ultrasonic technology alone due to the uncertainty ofknowing when the seal was completed before initiating the cutting. Inone aspect, the CTM algorithm may be configured to protect the endeffector clamp arm pad by allowing the temperature of the ultrasonicblade to exceed the temperature required for cutting (transecting) thetissue but not to exceed the melting point of the clamp arm pad. Inanother aspect, the CTM seal only algorithm may be tuned to exceed thesealing temperature of tissue (approximately 115° C. to approximately180° C. based on experimentation) but not to exceed the cutting(transecting) temperature of tissue (approximately 180° C. toapproximately 350° C.). In the latter configuration, the CTM seal onlyalgorithm provides a “seal only” tissue effect that has beensuccessfully demonstrated. In a linear fit that calculates the change infrequency with respect to the initial lock frequency, as shown in FIG.23, for example, changing the intercept of the fit regulates the finalsteady state temperature of the ultrasonic blade. By adjusting theintercept parameter, the ultrasonic blade can be set to never exceedapproximately 180° C. resulting in the tissue sealing but not cutting.In one aspect, increasing the clamp force may improve the sealingprocess without impacting clamp arm pad burn through because thetemperature of the blade is controlled by the CTM seal only algorithm.As previously described, the CTM seal only algorithm may be implementedby the generator and PID controller described with reference to FIGS. 2,7, 8A-8C, 9A-9B, and 16-17, for example. Accordingly, the flow diagram133320 shown in FIG. 25 may be modified such that the control circuitcalculates 133326 a new lower frequency limit (threshold t correspondwith a “seal only” temperature such as, for example, approximately 180°C., determine 133328 when the frequency is near the lower limit, andregulate 133332 the temperature until the “seal only” surgical procedureis terminated and the ultrasonic transducer is deactivated.

In another aspect, the present disclosure provides a cool thermalmonitoring (CTMo) algorithm configured to detect when atraumaticgrasping is feasible. Acoustic ultrasonic energy results in anultrasonic blade temperature of approximately 230° C. to approximately300° C. to achieve the desired effect of cutting or transecting tissue.Because heat is retained in the metal body of the ultrasonic blade for aperiod of time after deactivation of the ultrasonic transducer, theresidual heat stored in the ultrasonic blade can cause tissue damage ifthe ultrasonic end effector is used to grasp tissue before theultrasonic blade has had an opportunity to cool down.

In one aspect, the CTMo algorithm calculates a change in the naturalfrequency of the ultrasonic electromechanical system from the naturalfrequency at a hot state to a natural frequency at a temperature whereatraumatic grasping is possible without damaging the tissue grasped bythe end effector. Directly or a predetermined period of time afteractivating the ultrasonic transducer, a non-therapeutic signal(approximately 5 mA) is applied to the ultrasonic transducer containinga bandwidth of frequencies, approximately 48,000 Hz to 52,000 Hz, forexample, at which the natural frequency is expected to be found. A FFTalgorithm, or other mathematically efficient algorithm of detecting thenatural frequency of the ultrasonic electromechanical system, of theimpedance of the ultrasonic transducer measured during the stimulationof the ultrasonic transducer with the non-therapeutic signal willindicate the natural frequency of the ultrasonic blade as being thefrequency at which the impedance magnitude is at a minimum. Continuallystimulating the ultrasonic transducer in this manner provides continualfeedback of the natural frequency of the ultrasonic blade within afrequency resolution of the FFT or other algorithm for estimating ormeasuring the natural frequency. When a change in natural frequency isdetected that corresponds to a temperature that is feasible foratraumatic grasping, a tone, or a LED, or an on screen display or otherform of notification, or a combination thereof, is provided to indicatethat the device is capable of atraumatic grasping.

In another aspect, the present disclosure provides a CTM algorithmconfigured to tone for seal and end of cut or transection. Providing“tissue sealed” and “end of cut” notifications is a challenge forconventional ultrasonic devices because temperature measurement cannoteasily be directly mounted to the ultrasonic blade and the clamp arm padis not explicitly detected by the blade using sensors. A CTM algorithmcan indicate temperature state of the ultrasonic blade and can beemployed to indicate the “end of cut” or “tissue sealed”\”, or both,states because these are temperature-based events.

In one aspect, a CTM algorithm according to the present disclosuredetects the “end of cut” state and activates a notification. Tissuetypically cuts at approximately 210° C. to approximately 320° C. withhigh probability. A CTM algorithm can activate a tone at 320° C. (orsimilar) to indicate that further activation on the tissue is notproductive as that the tissue is probably cut and the ultrasonic bladeis now running against the clamp arm pad, which is acceptable when theCTM algorithm is active because it controls the temperature of theultrasonic blade. In one aspect, the CTM algorithm is programmed tocontrol or regulate power to the ultrasonic transducer to maintain thetemperature of the ultrasonic blade to approximately 320° C. when thetemperature of the ultrasonic blade is estimated to have reached 320° C.Initiating a tone at this point provides an indication that the tissuehas been cut. The CTM algorithm is based on a variation in frequencywith temperature. After determining an initial state temperature (basedon initial frequency), the CTM algorithm can calculate a frequencychange that corresponds to a temperature that implies when the tissue iscut. For example, if the starting frequency is 51,000 Hz, the CTMalgorithm will calculate the change in frequency required to achieve320° C. which might be −112 Hz. It will then initiate control tomaintain that frequency set point (e.g., 50,888 Hz) thereby regulatingthe temperature of the ultrasonic blade. Similarly, a frequency changecan be calculated based on an initial frequency that indicates when theultrasonic blade is at a temperature which indicates that the tissue isprobably cut. At this point, the CTM algorithm does not have to controlpower, but simply initiate a tone to indicate the state of the tissue orthe CTM algorithm can control frequency at this point to maintain thattemperature if desired. Either way, the “end of cut” is indicated.

In one aspect, a CTM algorithm according to the present disclosuredetects the “tissue sealed” state and activates a notification. Similarto the end of cut detection, tissue seals between approximately 105° C.and approximately 200° C. The change in frequency from an initialfrequency required to indicate that a temperature of the ultrasonicblade has reached 200° C., which indicates a seal only state, can becalculated at the onset of activation of the ultrasonic transducer. TheCTM algorithm can activate a tone at this point and if the surgeonwishes to obtain a seal only state, the surgeon could stop activation orto achieve a seal only state the surgeon could stop activation of theultrasonic transducer and automatically initiate a specific seal onlyalgorithm from this point on or the surgeon could continue activation ofthe ultrasonic transducer to achieve a tissue cut state.

Application of Smart Ultrasonic Blade Technology

When an ultrasonic blade is immersed in a fluid-filled surgical field,the ultrasonic blade cools down during activation rendering lesseffective for sealing and cutting tissue in contact therewith. Thecooling down of the ultrasonic blade may lead to longer activation timesand/or hemostasis issues because adequate heat is not delivered to thetissue. In order to overcome the cooling of the ultrasonic blade, moreenergy delivery may be required to shorten the transection times andachieve suitable hemostasis under these fluid immersion conditions.Using a frequency-temperature feedback control system, if the ultrasonicblade temperature is detected to, either start out below, or remainbelow a certain temperature for a certain period of time, the outputpower of the generator can be increased to compensate for cooling due toblood/saline/other fluid present in the surgical field.

Accordingly, the frequency-temperature feedback control system describedherein can improve the performance of an ultrasonic device especiallywhen the ultrasonic blade is located or immersed, partially or wholly,in a fluid-filled surgical field. The frequency-temperature feedbackcontrol system described herein minimizes long activation times and/orpotential issues with ultrasonic device performance in fluid-filledsurgical field.

As previously described, the temperature of the ultrasonic blade may beinferred by detecting the impedance of the ultrasonic transducer givenby the following expression:

${Z_{g}(t)} = \frac{V_{g}(t)}{I_{g}(t)}$or equivalently, detecting the phase angle φ between the voltageV_(g)(t) and current I_(g)(t) signals applied to the ultrasonictransducer. The phase angle φ information also may be used to infer theconditions of the ultrasonic blade. As discussed with particularityherein, the phase angle φ changes as a function of the temperature ofthe ultrasonic blade. Therefore, the phase angle φ information may beemployed to control the temperature of the ultrasonic blade. This may bedone, for example, by reducing the power delivered to the ultrasonicblade when the ultrasonic blade runs too hot and increasing the powerdelivered to the ultrasonic blade when the ultrasonic blade runs toocold. FIGS. 27A-27B are graphical representations of temperaturefeedback control for adjusting ultrasonic power applied to an ultrasonictransducer when a sudden drop in temperature of an ultrasonic blade isdetected.

FIG. 27A is a graphical representation of ultrasonic power output 133070as a function of time, in accordance with at least one aspect of thepresent disclosure. Power output of the ultrasonic generator is shownalong the vertical axis and time (sec) is shown along the horizontalaxis. FIG. 27B is a graphical representation of ultrasonic bladetemperature 133080 as a function of time, in accordance with at leastone aspect of the present disclosure. Ultrasonic blade temperature isshown along the vertical axis and time (sec) is shown along thehorizontal axis. The temperature of the ultrasonic blade increases withthe application of constant power 133072 as shown in FIG. 27A. Duringuse, the temperature of the ultrasonic blade may suddenly drop 133084.This may result from a variety of conditions, however, during use, itmay be inferred that the temperature of the ultrasonic blade drops whenit is immersed in a fluid-filled surgical field (e.g., blood, saline,water, etc.). At time to, the temperature of the ultrasonic blade 133086drops below the desired minimum temperature 133082 and thefrequency-temperature feedback control algorithm detects the drop intemperature and begins to increase or “ramp up” the power as shown bythe power ramp 133074 delivered to the ultrasonic blade to start raisingthe temperature of the ultrasonic blade above the desired minimumtemperature 133082.

With reference to FIGS. 27A and 27B, the ultrasonic generator is outputssubstantially constant power 133072 as long the temperature of theultrasonic blade 133084 remains above the desired minimum temperature133082. At t₀, processor or control circuit in the generator orinstrument or both detects the drop in temperature of the ultrasonicblade 133086 below the desired minimum temperature 133082 and initiatesa frequency-temperature feedback control algorithm to raise thetemperature of the ultrasonic blade above the minimum desiredtemperature 133082. Accordingly, the generator power begins to ramp133074 at ti corresponding to the detection of a sudden drop in thetemperature of the ultrasonic blade at to. Under thefrequency-temperature feedback control algorithm, the power continues toramp 133074 until the temperature of the ultrasonic blade is above thedesired minimum temperature 133082.

FIG. 28 is a logic flow diagram 133090 of a process depicting a controlprogram or a logic configuration to control the temperature of anultrasonic blade, in accordance with at least one aspect of the presentdisclosure. According to the process, the processor or control circuitof the generator or instrument or both executes one aspect of afrequency-temperature feedback control algorithm discussed in connectionwith FIGS. 27A and 27B to apply 133092 a power level to the ultrasonictransducer to achieve a desired temperature at the ultrasonic blade. Thegenerator monitors 133094 the phase angle φ between the voltage V_(g)(t)and current I_(g)(t) signals applied to drive the ultrasonic transducer.Based on the phase angle φ, the generator infers 133096 the temperatureof the ultrasonic blade using the techniques described herein inconnection with FIGS. 19A-21. The generator determines 133098 whetherthe temperature of the ultrasonic blade is below a desired minimumtemperature by comparing the inferred temperature of the ultrasonicblade to a predetermined desired temperature. The generator then adjuststhe power level applied to the ultrasonic transducer based on thecomparison. For example, the process continues along NO branch when thetemperature of the ultrasonic blade is at or above the desired minimumtemperature and continues along YES branch when the temperature of theultrasonic blade is below the desired minimum temperature. When thetemperature of the ultrasonic blade is below the desired minimumtemperature, the generator increases 133100 the power level to theultrasonic transducer, e.g., by increasing the voltage V_(g)(t) and/orcurrent I_(g)(t) signals, to raise the temperature of the ultrasonicblade and continues increasing the power level applied to the ultrasonictransducer until the temperature of the ultrasonic blade increases abovethe minimum desired temperature.

Adaptive Advanced Tissue Treatment Pad Saver Mode

FIG. 29 is a graphical representation 133110 of ultrasonic bladetemperature as a function of time during a vessel firing, in accordancewith at least one aspect of the present disclosure. A plot 133112 ofultrasonic blade temperature is graphed along the vertical axis as afunction of time along the horizontal axis. The frequency-temperaturefeedback control algorithm combines the temperature of the ultrasonicblade feedback control with the jaw sensing ability. Thefrequency-temperature feedback control algorithm provides optimalhemostasis balanced with device durability and can deliver energyintelligently for best sealing while protecting the clamp arm pad.

As shown in FIG. 29, the optimum temperature 133114 for vessel sealingis marked as a first target temperature T₁ and the optimum temperature133116 for “infinite” clamp arm pad life is marked as a second targettemperature T₂. The frequency-temperature feedback control algorithminfers the temperature of the ultrasonic blade and maintains thetemperature of the ultrasonic blade between the first and second targettemperature thresholds T₁ and T₂. The generator power output is thusdriven to achieve optimal ultrasonic blade temperatures for sealingvessels and prolonging the life of the clamp arm pad.

Initially, the temperature of the ultrasonic blade increases as theblade heats up and eventually exceeds the first target temperaturethreshold T₁. The frequency-temperature feedback control algorithm takesover to control the temperature of the blade to T₁ until the vesseltransection is completed 133118 at t₀ and the ultrasonic bladetemperature drops below the second target temperature threshold T₂. Aprocessor or control circuit of the generator or instrument or bothdetects when the ultrasonic blade contacts the clamp arm pad. Once thevessel transection is completed at t₀ and detected, thefrequency-temperature feedback control algorithm switches to controllingthe temperature of the ultrasonic blade to the second target thresholdT₂ to prolong the life of the clam arm pad. The optimal clamp arm padlife temperature for a TEFLON clamp arm pad is approximately 325° C. Inone aspect, the advanced tissue treatment can be announced to the userat a second activation tone.

FIG. 30 is a logic flow diagram 133120 of a process depicting a controlprogram or a logic configuration to control the temperature of anultrasonic blade between two temperature set points as depicted in FIG.29, in accordance with at least one aspect of the present disclosure.According to the process, the generator executes one aspect of thefrequency-temperature feedback control algorithm to apply 133122 a firstpower level to the ultrasonic transducer, e.g., by adjusting the voltageV_(g)(t) and/or the current I_(g)(t) signals applied to the ultrasonictransducer, to set the ultrasonic blade temperature to a first target T₁optimized for vessel sealing. As previously described, the generatormonitors 133124 the phase angle φ between the voltage V_(g)(t) andcurrent I_(g)(t) signals applied to the ultrasonic transducer and basedon the phase angle φ, the generator infers 133126 the temperature of theultrasonic blade using the techniques described herein in connectionwith FIGS. 19A-21. According to the frequency-temperature feedbackcontrol algorithm, a processor or control circuit of the generator orinstrument or both maintains the ultrasonic blade temperature at thefirst target temperature T₁ until the transection is completed. Thefrequency-temperature feedback control algorithm may be employed todetect the completion of the vessel transection process. The processoror control circuit of the generator or instrument or both determines133128 when the vessel transection is complete. The process continuesalong NO branch when the vessel transection is not complete andcontinues along YES branch when the vessel transection is complete.

When the vessel transection in not complete, the processor or controlcircuit of the generator or instrument or both determines 133130 if thetemperature of the ultrasonic blade is set at temperature T₁ optimizedfor vessel sealing and transecting. If the ultrasonic blade temperatureis set at T₁, the process continues along the YES branch and theprocessor or control circuit of the generator or instrument or bothcontinues to monitor 133124 the phase angle φ between the voltageV_(g)(t) and current I_(g)(t) signals applied to the ultrasonictransducer and based on the phase angle φ. If the ultrasonic bladetemperature is not set at T₁, the process continues along NO branch andthe processor or control circuit of the generator or instrument or bothcontinues to apply 133122 a first power level to the ultrasonictransducer.

When the vessel transection is complete, the processor or controlcircuit of the generator or instrument or both applies 133132 a secondpower level to the ultrasonic transducer to set the ultrasonic blade toa second target temperature T₂ optimized for preserving or extending thelife of the clamp arm pad. The processor or control circuit of thegenerator or instrument or both determines 133134 if the temperature ofthe ultrasonic blade is at set temperature T₂. If the temperature of theultrasonic blade is set at T₂, the process completes 133136 the vesseltransection procedure.

Start Temperature of Blade

Knowing the temperature of the ultrasonic blade at the beginning of atransection can enable the generator to deliver the proper quantity ofpower to heat up the blade for a quick cut or if the blade is alreadyhot add only as much power as would be needed. This technique canachieve more consistent transection times and extend the life of theclam arm pad (e.g., a TEFLON clamp arm pad). Knowing the temperature ofthe ultrasonic blade at the beginning of the transection can enable thegenerator to deliver the right amount of power to the ultrasonictransducer to generate a desired amount of displacement of theultrasonic blade.

FIG. 31 is a logic flow diagram 133140 of a process depicting a controlprogram or a logic configuration to determine the initial temperature ofan ultrasonic blade, in accordance with at least one aspect of thepresent disclosure. To determine the initial temperature of anultrasonic blade, at the manufacturing plant, the resonant frequenciesof ultrasonic blades are measured at room temperature or at apredetermined ambient temperature. The baseline frequency values arerecorded and stored in a lookup table of the generator or instrument orboth. The baseline values are used to generate a transfer function. Atthe start of an ultrasonic transducer activation cycle, the generatormeasures 133142 the resonant frequency of the ultrasonic blade andcompares 133144 the measured resonant frequency to the baseline resonantfrequency value and determines the difference in frequency (Δf). The Δfis compared to the lookup table or transfer function for correctedultrasonic blade temperature. The resonant frequency of the ultrasonicblade may be determined by sweeping the frequency of the voltageV_(g)(t) and current I_(g)(t) signals applied to the ultrasonictransducer. The resonant frequency is that frequency at which the phaseangle φ voltage V_(g)(t) and current I_(g)(t) signals is zero asdescribed herein.

Once the resonant frequency of the ultrasonic blade is determined, theprocessor or control circuit of the generator or instrument or bothdetermines 133146 the initial temperature of the ultrasonic blade basedon the difference between the measured resonant frequency and thebaseline resonant frequency. The generator sets the power leveldelivered the ultrasonic transducer, e.g., by adjusting the voltageV_(g)(t) or current I_(g)(t) drive signals or both, to one of thefollowing values prior to activating the ultrasonic transducer.

The processor or control circuit of the generator or instrument or bothdetermines 133148 if the initial temperature of the ultrasonic blade islow. If the initial temperature of the ultrasonic blade is low, theprocess continues along YES branch and the processor or control circuitof the generator or instrument or both applies 133152 a high power levelto the ultrasonic transducer to increase the temperature of theultrasonic blade and completes 133156 the vessel transection procedure.

If the initial temperature of the ultrasonic blade is not low, theprocess continues along NO branch and the processor or control circuitof the generator or instrument or both determines 133150 if the initialtemperature of the ultrasonic blade is high. If the initial temperatureof the ultrasonic blade is high, the process proceeds along YES branchand the processor or control circuit of the generator or instrument orboth applies 133154 a low power level to the ultrasonic transducer todecrease the temperature of the ultrasonic blade and completes 133156the vessel transection procedure. If the initial temperature of theultrasonic blade is not high, the process continues along NO branch andthe processor or control circuit of the generator or instrument or bothcompletes 133156 the vessel transection.

Smart Blade Technology to Control Blade Instability

The temperature of an ultrasonic blade and the contents within the jawsof an ultrasonic end effector can be determined using thefrequency-temperature feedback control algorithms described herein. Thefrequency/temperature relationship of the ultrasonic blade is employedto control ultrasonic blade instability with temperature.

As described herein, there is a well-known relationship between thefrequency and temperature in ultrasonic blades. Some ultrasonic bladesexhibit displacement instability or modal instability in the presence ofincreasing temperature. This known relationship may be employed tointerpret when an ultrasonic blade is approaching instability and thenadjusting the power level driving the ultrasonic transducer (e.g., byadjusting the driving voltage V_(g)(t) or current I_(g)(t) signals, orboth, applied to the ultrasonic transducer) to modulate the temperatureof the ultrasonic blade to prevent instability of the ultrasonic blade.

FIG. 32 is a logic flow diagram 133160 of a process depicting a controlprogram or a logic configuration to determine when an ultrasonic bladeis approaching instability and then adjusting the power to theultrasonic transducer to prevent instability of the ultrasonictransducer, in accordance with at least one aspect of the presentdisclosure. The frequency/temperature relationship of an ultrasonicblade that exhibits a displacement or modal instability is mapped bysweeping the frequency of the drive voltage V_(g)(t) or current I_(g)(t)signals, or both, over the temperature of the ultrasonic blade andrecording the results. A function or relationship is developed that canbe used/interpreted by a control algorithm executed by the generator.Trigger points can be established using the relationship to notify thegenerator that an ultrasonic blade is approaching the known bladeinstability. The generator executes a frequency-temperature feedbackcontrol algorithm processing function and closed loop response such thatthe driving power level is reduced (e.g., by lowering the drivingvoltage V_(g)(t) or current I_(g)(t), or both, applied to the ultrasonictransducer) to modulate the temperature of the ultrasonic blade at orbelow the trigger point to prevent a given blade from reachinginstability.

Advantages include simplification of ultrasonic blade configurationssuch that the instability characteristics of the ultrasonic blade do notneed to be designed out and can be compensated using the presentinstability control technique. The present instability control techniquealso enables new ultrasonic blade geometries and can improve stressprofile in heated ultrasonic blades. Additionally, ultrasonic blades canbe configured to diminish performance of the ultrasonic blade if usedwith generators that do not employ this technique.

In accordance with the process depicted by the logic flow diagram133160, the processor or control circuit of the generator or instrumentor both monitors 133162 the phase angle φ between the voltage V_(g)(t)and current I_(g)(t) signals applied to the ultrasonic transducer. Theprocessor or control circuit of the generator or instrument or bothinfers 133164 the temperature of the ultrasonic blade based on the phaseangle φ between the voltage V_(g)(t) and current I_(g)(t) signalsapplied to the ultrasonic transducer. The processor or control circuitof the generator or instrument or both compares 133166 the inferredtemperature of the ultrasonic blade to an ultrasonic blade instabilitytrigger point threshold. The processor or control circuit of thegenerator or instrument or both determines 133168 whether the ultrasonicblade is approaching instability. If not, the process proceed along theNO branch and monitors 133162 the phase angle φ, infers 133164 thetemperature of the ultrasonic blade, and compares 133166 the inferredtemperature of the ultrasonic blade to an ultrasonic blade instabilitytrigger point threshold until the ultrasonic blade approachesinstability. The process then proceeds along the YES branch and theprocessor or control circuit of the generator or instrument or bothadjusts 133170 the power level applied to the ultrasonic transducer tomodulate the temperature of the ultrasonic blade.

Ultrasonic Sealing Algorithm with Temperature Control

Ultrasonic sealing algorithms for ultrasonic blade temperature controlcan be employed to improve hemostasis utilizing a frequency-temperaturefeedback control algorithm described herein to exploit thefrequency/temperature relationship of ultrasonic blades.

In one aspect, a frequency-temperature feedback control algorithm may beemployed to alter the power level applied to the ultrasonic transducerbased on measured resonant frequency (using spectroscopy) which relatesto temperature, as described in various aspects of the presentdisclosure. In one aspect, the frequency-temperature feedback controlalgorithm may be activated by an energy button on the ultrasonicinstrument.

It is known that optimal tissue effects may be obtained by increasingthe power level driving the ultrasonic transducer (e.g., by increasingthe driving voltage V_(g)(t) or current I_(g)(t), or both, applied tothe ultrasonic transducer) early on in the sealing cycle to rapidly heatand desiccate the tissue, then lowering the power level driving theultrasonic transducer (e.g., by lowering the driving voltage V_(g)(t) orcurrent I_(g)(t), or both, applied to the ultrasonic transducer) toslowly allow the final seal to form. In one aspect, afrequency-temperature feedback control algorithm according to thepresent disclosure sets a limit on the temperature threshold that thetissue can reach as the tissue heats up during the higher power levelstage and then reduces the power level to control the temperature of theultrasonic blade based on the melting point of the clamp jaw pad (e.g.,TEFLON) to complete the seal. The control algorithm can be implementedby activating an energy button on the instrument for a moreresponsive/adaptive sealing to reduce more the complexity of thehemostasis algorithm.

FIG. 33 is a logic flow diagram 133180 of a process depicting a controlprogram or a logic configuration to provide ultrasonic sealing withtemperature control, in accordance with at least one aspect of thepresent disclosure. According to the control algorithm, the processor orcontrol circuit of the generator or instrument or both activates 133182ultrasonic blade sensing using spectroscopy (e.g., smart blade) andmeasures 133184 the resonant frequency of the ultrasonic blade (e.g.,the resonant frequency of the ultrasonic electromechanical system) todetermine the temperature of the ultrasonic blade using afrequency-temperature feedback control algorithm (spectroscopy) asdescribed herein. As previously described, the resonant frequency of theultrasonic electromechanical system is mapped to obtain the temperatureof the ultrasonic blade as a function of resonant frequency of theelectromechanical ultrasonic system.

A first desired resonant frequency f_(x) of the ultrasonicelectromechanical system corresponds to a first desired temperature Z°of the ultrasonic blade. In one aspect, the first desired ultrasonicblade temperature Z° is an optimal temperature (e.g., 450° C.) fortissue coagulation. A second desired frequency f_(Y) of the ultrasonicelectromechanical system corresponds to a second desired temperature ZZ°of the ultrasonic blade. In one aspect, the second desired ultrasonicblade temperature ZZ° is a temperature of 330° C., which is below themelting point of the clamp arm pad, which is approximately 380° C. forTEFLON.

The processor or control circuit of the generator or instrument or bothcompares 133186 the measured resonant frequency of the ultrasonicelectromechanical system to the first desired frequency f_(x). In otherwords, the process determines whether the temperature of the ultrasonicblade is less than the temperature for optimal tissue coagulation. Ifthe measured resonant frequency of the ultrasonic electromechanicalsystem is less than the first desired frequency f_(x), the processcontinues along the NO branch and the processor or control circuit ofthe generator or instrument or both increases 133188 the power levelapplied to the ultrasonic transducer to increase the temperature of theultrasonic blade until the measured resonant frequency of the ultrasonicelectromechanical system exceeds the first desired frequency f_(x). Inwhich case, the tissue coagulation process is completed and the processcontrols the temperature of the ultrasonic blade to the second desiredtemperature corresponding to the second desired frequency f_(y).

The process continues along the YES branch and the processor or controlcircuit of the generator or instrument or both decreases 133190 thepower level applied to the ultrasonic transducer to decrease thetemperature of the ultrasonic blade. The processor or control circuit ofthe generator or instrument or both measures 133192 the resonantfrequency of the ultrasonic electromechanical system and compares 133194the measured resonant frequency to the second desired frequency f_(Y).If the measured resonant frequency is not less than the second desiredfrequency f_(Y), the processor or control circuit of the generator orinstrument or both decreases 133190 the ultrasonic power level until themeasured resonant frequency is less than the second desired frequencyf_(Y). The frequency-temperature feedback control algorithm to maintainthe measured resonant frequency of the ultrasonic electromechanicalsystem below the second desired frequency f_(y), e.g., the temperatureof the ultrasonic blade is less than the temperature of the meltingpoint of the clamp arm pad then, the generator executes the increasesthe power level applied to the ultrasonic transducer to increase thetemperature of the ultrasonic blade until the tissue transection processis complete 133196.

FIG. 34 is a graphical representation 133200 of ultrasonic transducercurrent and ultrasonic blade temperature as a function of time, inaccordance with at least one aspect of the present disclosure. FIG. 34illustrates the results of the application of the frequency-temperaturefeedback control algorithm described in FIG. 34. The graphicalrepresentation 133200 depicts a first plot 133202 of ultrasonic bladetemperature as a function of time with respect to a second plot 133204of ultrasonic transducer current I_(g)(t) as a function of time. Asshown, the transducer I_(g)(t) is maintained constant until theultrasonic blade temperature reaches 450°, which is an optimalcoagulation temperature. Once the ultrasonic blade temperature reaches450°, the frequency-temperature feedback control algorithm decrease thetransducer current I_(g)(t) until the temperature of the ultrasonicblade drops to below 330°, which is below the melting point of a TEFLONpad, for example.

While several forms have been illustrated and described, it is not theintention of the applicant to restrict or limit the scope of theappended claims to such detail. Numerous modifications, variations,changes, substitutions, combinations, and equivalents to those forms maybe implemented and will occur to those skilled in the art withoutdeparting from the scope of the present disclosure. Moreover, thestructure of each element associated with the described forms can bealternatively described as a means for providing the function performedby the element. Also, where materials are disclosed for certaincomponents, other materials may be used. It is therefore to beunderstood that the foregoing description and the appended claims areintended to cover all such modifications, combinations, and variationsas falling within the scope of the disclosed forms. The appended claimsare intended to cover all such modifications, variations, changes,substitutions, modifications, and equivalents.

The foregoing detailed description has set forth various forms of thedevices and/or processes via the use of block diagrams, flowcharts,and/or examples. Insofar as such block diagrams, flowcharts, and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts, and/or examples can beimplemented, individually and/or collectively, by a wide range ofhardware, software, firmware, or virtually any combination thereof.Those skilled in the art will recognize that some aspects of the formsdisclosed herein, in whole or in part, can be equivalently implementedin integrated circuits, as one or more computer programs running on oneor more computers (e.g., as one or more programs running on one or morecomputer systems), as one or more programs running on one or moreprocessors (e.g., as one or more programs running on one or moremicroprocessors), as firmware, or as virtually any combination thereof,and that designing the circuitry and/or writing the code for thesoftware and or firmware would be well within the skill of one of skillin the art in light of this disclosure. In addition, those skilled inthe art will appreciate that the mechanisms of the subject matterdescribed herein are capable of being distributed as one or more programproducts in a variety of forms, and that an illustrative form of thesubject matter described herein applies regardless of the particulartype of signal bearing medium used to actually carry out thedistribution.

Instructions used to program logic to perform various disclosed aspectscan be stored within a memory in the system, such as dynamic randomaccess memory (DRAM), cache, flash memory, or other storage.Furthermore, the instructions can be distributed via a network or by wayof other computer readable media. Thus a machine-readable medium mayinclude any mechanism for storing or transmitting information in a formreadable by a machine (e.g., a computer), but is not limited to, floppydiskettes, optical disks, compact disc, read-only memory (CD-ROMs), andmagneto-optical disks, read-only memory (ROMs), random access memory(RAM), erasable programmable read-only memory (EPROM), electricallyerasable programmable read-only memory (EEPROM), magnetic or opticalcards, flash memory, or a tangible, machine-readable storage used in thetransmission of information over the Internet via electrical, optical,acoustical or other forms of propagated signals (e.g., carrier waves,infrared signals, digital signals, etc.). Accordingly, thenon-transitory computer-readable medium includes any type of tangiblemachine-readable medium suitable for storing or transmitting electronicinstructions or information in a form readable by a machine (e.g., acomputer).

As used in any aspect herein, the term “control circuit” may refer to,for example, hardwired circuitry, programmable circuitry (e.g., acomputer processor comprising one or more individual instructionprocessing cores, processing unit, processor, microcontroller,microcontroller unit, controller, digital signal processor (DSP),programmable logic device (PLD), programmable logic array (PLA), orfield programmable gate array (FPGA)), state machine circuitry, firmwarethat stores instructions executed by programmable circuitry, and anycombination thereof. The control circuit may, collectively orindividually, be embodied as circuitry that forms part of a largersystem, for example, an integrated circuit (IC), an application-specificintegrated circuit (ASIC), a system on-chip (SoC), desktop computers,laptop computers, tablet computers, servers, smart phones, etc.Accordingly, as used herein “control circuit” includes, but is notlimited to, electrical circuitry having at least one discrete electricalcircuit, electrical circuitry having at least one integrated circuit,electrical circuitry having at least one application specific integratedcircuit, electrical circuitry forming a general purpose computing deviceconfigured by a computer program (e.g., a general purpose computerconfigured by a computer program which at least partially carries outprocesses and/or devices described herein, or a microprocessorconfigured by a computer program which at least partially carries outprocesses and/or devices described herein), electrical circuitry forminga memory device (e.g., forms of random access memory), and/or electricalcircuitry forming a communications device (e.g., a modem, communicationsswitch, or optical-electrical equipment). Those having skill in the artwill recognize that the subject matter described herein may beimplemented in an analog or digital fashion or some combination thereof.

As used in any aspect herein, the term “logic” may refer to an app,software, firmware and/or circuitry configured to perform any of theaforementioned operations. Software may be embodied as a softwarepackage, code, instructions, instruction sets and/or data recorded onnon-transitory computer readable storage medium. Firmware may beembodied as code, instructions or instruction sets and/or data that arehard-coded (e.g., nonvolatile) in memory devices.

As used in any aspect herein, the terms “component,” “system,” “module”and the like can refer to a computer-related entity, either hardware, acombination of hardware and software, software, or software inexecution.

As used in any aspect herein, an “algorithm” refers to a self-consistentsequence of steps leading to a desired result, where a “step” refers toa manipulation of physical quantities and/or logic states which may,though need not necessarily, take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. It is common usage to refer to these signals asbits, values, elements, symbols, characters, terms, numbers, or thelike. These and similar terms may be associated with the appropriatephysical quantities and are merely convenient labels applied to thesequantities and/or states.

A network may include a packet switched network. The communicationdevices may be capable of communicating with each other using a selectedpacket switched network communications protocol. One examplecommunications protocol may include an Ethernet communications protocolwhich may be capable permitting communication using a TransmissionControl Protocol/Internet Protocol (TCP/IP). The Ethernet protocol maycomply or be compatible with the Ethernet standard published by theInstitute of Electrical and Electronics Engineers (IEEE) titled “IEEE802.3 Standard”, published in December, 2008 and/or later versions ofthis standard. Alternatively or additionally, the communication devicesmay be capable of communicating with each other using an X.25communications protocol. The X.25 communications protocol may comply orbe compatible with a standard promulgated by the InternationalTelecommunication Union-Telecommunication Standardization Sector(ITU-T). Alternatively or additionally, the communication devices may becapable of communicating with each other using a frame relaycommunications protocol. The frame relay communications protocol maycomply or be compatible with a standard promulgated by ConsultativeCommittee for International Telegraph and Telephone (CCITT) and/or theAmerican National Standards Institute (ANSI). Alternatively oradditionally, the transceivers may be capable of communicating with eachother using an Asynchronous Transfer Mode (ATM) communications protocol.The ATM communications protocol may comply or be compatible with an ATMstandard published by the ATM Forum titled “ATM-MPLS NetworkInterworking 2.0” published August 2001, and/or later versions of thisstandard. Of course, different and/or after-developedconnection-oriented network communication protocols are equallycontemplated herein.

Unless specifically stated otherwise as apparent from the foregoingdisclosure, it is appreciated that, throughout the foregoing disclosure,discussions using terms such as “processing,” “computing,”“calculating,” “determining,” “displaying,” or the like, refer to theaction and processes of a computer system, or similar electroniccomputing device, that manipulates and transforms data represented asphysical (electronic) quantities within the computer system's registersand memories into other data similarly represented as physicalquantities within the computer system memories or registers or othersuch information storage, transmission or display devices.

One or more components may be referred to herein as “configured to,”“configurable to,” “operable/operative to,” “adapted/adaptable,” “ableto,” “conformable/conformed to,” etc. Those skilled in the art willrecognize that “configured to” can generally encompass active-statecomponents and/or inactive-state components and/or standby-statecomponents, unless context requires otherwise.

The terms “proximal” and “distal” are used herein with reference to aclinician manipulating the handle portion of the surgical instrument.The term “proximal” refers to the portion closest to the clinician andthe term “distal” refers to the portion located away from the clinician.It will be further appreciated that, for convenience and clarity,spatial terms such as “vertical”, “horizontal”, “up”, and “down” may beused herein with respect to the drawings. However, surgical instrumentsare used in many orientations and positions, and these terms are notintended to be limiting and/or absolute.

Those skilled in the art will recognize that, in general, terms usedherein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to claims containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations.

In addition, even if a specific number of an introduced claim recitationis explicitly recited, those skilled in the art will recognize that suchrecitation should typically be interpreted to mean at least the recitednumber (e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that typically a disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms unless context dictates otherwise. For example, the phrase “Aor B” will be typically understood to include the possibilities of “A”or “B” or “A and B.”

With respect to the appended claims, those skilled in the art willappreciate that recited operations therein may generally be performed inany order. Also, although various operational flow diagrams arepresented in a sequence(s), it should be understood that the variousoperations may be performed in other orders than those which areillustrated, or may be performed concurrently. Examples of suchalternate orderings may include overlapping, interleaved, interrupted,reordered, incremental, preparatory, supplemental, simultaneous,reverse, or other variant orderings, unless context dictates otherwise.Furthermore, terms like “responsive to,” “related to,” or otherpast-tense adjectives are generally not intended to exclude suchvariants, unless context dictates otherwise.

It is worthy to note that any reference to “one aspect,” “an aspect,”“an exemplification,” “one exemplification,” and the like means that aparticular feature, structure, or characteristic described in connectionwith the aspect is included in at least one aspect. Thus, appearances ofthe phrases “in one aspect,” “in an aspect,” “in an exemplification,”and “in one exemplification” in various places throughout thespecification are not necessarily all referring to the same aspect.Furthermore, the particular features, structures or characteristics maybe combined in any suitable manner in one or more aspects.

Any patent application, patent, non-patent publication, or otherdisclosure material referred to in this specification and/or listed inany Application Data Sheet is incorporated by reference herein, to theextent that the incorporated materials is not inconsistent herewith. Assuch, and to the extent necessary, the disclosure as explicitly setforth herein supersedes any conflicting material incorporated herein byreference. Any material, or portion thereof, that is said to beincorporated by reference herein, but which conflicts with existingdefinitions, statements, or other disclosure material set forth hereinwill only be incorporated to the extent that no conflict arises betweenthat incorporated material and the existing disclosure material.

In summary, numerous benefits have been described which result fromemploying the concepts described herein. The foregoing description ofthe one or more forms has been presented for purposes of illustrationand description. It is not intended to be exhaustive or limiting to theprecise form disclosed. Modifications or variations are possible inlight of the above teachings. The one or more forms were chosen anddescribed in order to illustrate principles and practical application tothereby enable one of ordinary skill in the art to utilize the variousforms and with various modifications as are suited to the particular usecontemplated. It is intended that the claims submitted herewith definethe overall scope.

Various aspects of the subject matter described herein are set out inthe following numbered examples:

Example 1. A method for controlling a temperature of an ultrasonicblade, the method comprising: determining, by a control circuit coupledto a memory, an actual resonant frequency of an ultrasonicelectromechanical system comprising an ultrasonic transducer coupled toan ultrasonic blade by an ultrasonic waveguide, wherein the actualresonant frequency is correlated to an actual temperature of theultrasonic blade; retrieving, from the memory by the control circuit, areference resonant frequency of the ultrasonic electromechanical system,wherein the reference resonant frequency is correlated to a referencetemperature of the ultrasonic blade; inferring, by the control circuit,the temperature of the ultrasonic blade based on the difference betweenthe actual resonant frequency and the reference resonant frequency; andcontrolling, by the control circuit, the temperature of the ultrasonicblade based on the inferred temperature.

Example 2. The method of Example 1, wherein determining, by the controlcircuit, the actual resonant frequency of the ultrasonicelectromechanical system comprises: determining, by the control circuit,a phase angle φ between a voltage V_(g)(t) and a current I_(g)(t) signalapplied to the ultrasonic transducer.

Example 3. The method of Example 2, further comprising generating, bythe control circuit, a temperature estimator and state space model ofthe inferred temperature of the ultrasonic blade as a function of theresonant frequency of the ultrasonic electromechanical system based on aset of non-linear state space equations.

Example 4. The method of Example 3, wherein the state space model isdefined by:

$\begin{bmatrix}{\overset{.}{F}}_{n} \\\overset{.}{T}\end{bmatrix} = {f\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$$\overset{.}{y} = {{h\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}.}$

Example 5. The method of Example 4, further comprising applying, by thecontrol circuit, a Kalman filter to improve the temperature estimatorand state space model.

Example 6. The method of Example 5, further comprising: applying, by thecontrol circuit, a state estimator in a feedback loop of the Kalmanfilter; controlling, by the control circuit, power applied to theultrasonic transducer; and regulating, by the control circuit, thetemperature of the ultrasonic blade.

Example 7. The method of Example 6, wherein a state variance of thestate estimator of the Kalman filter is defined by:(σ_(k) ⁻)²=σ_(k-1) ²+σ_(P) _(k) ² and

a gain K of the Kalman filter is defined by:

$K = {\frac{\left( \sigma_{k}^{-} \right)^{2}}{\left( \sigma_{k}^{-} \right)^{2} + \sigma_{m}^{2}}.}$

Example 8. The method of Example 1, wherein the control circuit andmemory are located at a surgical hub in communication with theultrasonic electromechanical system.

Example 9. A generator for controlling a temperature of an ultrasonicblade, the generator comprising: a control circuit coupled to a memory,the control circuit configured to: determine an actual resonantfrequency of an ultrasonic electromechanical system comprising anultrasonic transducer coupled to an ultrasonic blade by an ultrasonicwaveguide, wherein the actual resonant frequency is correlated to anactual temperature of the ultrasonic blade; retrieve from the memory areference resonant frequency of the ultrasonic electromechanical system,wherein the reference resonant frequency is correlated to a referencetemperature of the ultrasonic blade; infer the temperature of theultrasonic blade based on the difference between the actual resonantfrequency and the reference resonant frequency; and control thetemperature of the ultrasonic blade based on the inferred temperature.

Example 10. The generator of Example 9, wherein to determine the actualresonant frequency of the ultrasonic electromechanical system, thecontrol circuit is further configured to: determine a phase angle φbetween a voltage V_(g)(t) and a current I_(g)(t) signal applied to theultrasonic transducer.

Example 11. The generator of Example 10, wherein the control circuit isfurther configured to generate a temperature estimator and state spacemodel of the inferred temperature of the ultrasonic blade as a functionof the resonant frequency of the ultrasonic electromechanical systembased on a set of non-linear state space equations.

Example 12. The generator of Example 11, wherein the state space modelis defined by:

$\begin{bmatrix}{\overset{.}{F}}_{n} \\\overset{.}{T}\end{bmatrix} = {f\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$$\overset{.}{y} = {{h\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}.}$

Example 13. The generator of Example 12, wherein the control circuit isfurther configured to apply a Kalman filter to improve the temperatureestimator and state space model.

Example 14. The generator of Example 13, wherein the control circuit isfurther configured to: apply a state estimator in a feedback loop of theKalman filter; control power applied to the ultrasonic transducer; andregulate the temperature of the ultrasonic blade.

Example 15. The generator of Example 14, wherein a state variance of thestate estimator of the Kalman filter is defined by:(σ_(k) ⁻)²=σ_(k-1) ²+σ_(P) _(k) ² and

a gain K of the Kalman filter is defined by:

$K = {\frac{\left( \sigma_{k}^{-} \right)^{2}}{\left( \sigma_{k}^{-} \right)^{2} + \sigma_{m}^{2}}.}$

Example 16. The generator of Example 9, wherein the control circuit andmemory are located at a surgical hub in communication with thegenerator.

Example 17. An ultrasonic device for controlling a temperature of anultrasonic blade, the ultrasonic device comprising: a control circuitcoupled to a memory, the control circuit configured to: determine anactual resonant frequency of an ultrasonic electromechanical systemcomprising an ultrasonic transducer coupled to an ultrasonic blade by anultrasonic waveguide, wherein the actual resonant frequency iscorrelated to an actual temperature of the ultrasonic blade; retrievefrom the memory a reference resonant frequency of the ultrasonicelectromechanical system, wherein the reference resonant frequency iscorrelated to a reference temperature of the ultrasonic blade; infer thetemperature of the ultrasonic blade based on the difference between theactual resonant frequency and the reference resonant frequency; andcontrol the temperature of the ultrasonic blade based on the inferredtemperature.

Example 18. The ultrasonic device of Example 17, wherein to determinethe actual resonant frequency of the ultrasonic electromechanicalsystem, the control circuit is further configured to: determine a phaseangle φ between a voltage V_(g)(t) and a current I_(g)(t) signal appliedto the ultrasonic transducer.

Example 19. The ultrasonic device of Example 18, wherein the controlcircuit is further configured to generate a temperature estimator andstate space model of the inferred temperature of the ultrasonic blade asa function of the resonant frequency of the ultrasonic electromechanicalsystem based on a set of non-linear state space equations.

Example 20. The ultrasonic device of Example 19, wherein the state spacemodel is defined by:

$\begin{bmatrix}{\overset{.}{F}}_{n} \\\overset{.}{T}\end{bmatrix} = {f\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$$\overset{.}{y} = {{h\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}.}$

Example 21. The ultrasonic device of Example 20, wherein the controlcircuit is further configured to apply a Kalman filter to improve thetemperature estimator and state space model.

Example 22. The ultrasonic device of Example 21, wherein the controlcircuit is further configured to: apply a state estimator in a feedbackloop of the Kalman filter; control power applied to the ultrasonictransducer; and regulate the temperature of the ultrasonic blade.

Example 23. The ultrasonic device of Example 22, wherein a statevariance of the state estimator of the Kalman filter is defined by:(σ_(k) ⁻)²=σ_(k-1) ²+σ_(P) _(k) ² and

a gain K of the Kalman filter is defined by:

$K = {\frac{\left( \sigma_{k}^{-} \right)^{2}}{\left( \sigma_{k}^{-} \right)^{2} + \sigma_{m}^{2}}.}$

Example 24. The ultrasonic instrument of Example 17, wherein the controlcircuit and memory are located at a surgical hub in communication withthe ultrasonic instrument.

The invention claimed is:
 1. A method for controlling an estimatedtemperature of an ultrasonic blade, the method comprising: determining,by a control circuit coupled to a memory, an actual resonant frequencyof an ultrasonic electromechanical system comprising an ultrasonictransducer coupled to an ultrasonic blade by an ultrasonic waveguide,wherein the actual resonant frequency is correlated to an actualtemperature of the ultrasonic blade; retrieving, from the memory by thecontrol circuit, a reference resonant frequency of the ultrasonicelectromechanical system, wherein the reference resonant frequency iscorrelated to a reference temperature of the ultrasonic blade;inferring, by the control circuit, an inferred temperature of theultrasonic blade based on a difference between the actual resonantfrequency and the reference resonant frequency; controlling, by thecontrol circuit, the estimated temperature of the ultrasonic blade basedon the inferred temperature; generating, by the control circuit, atemperature estimator and a state space model of the inferredtemperature of the ultrasonic blade as a function of the actual resonantfrequency of the ultrasonic electromechanical system based on a set ofnon-linear state space equations; applying, by the control circuit, aKalman filter to improve the temperature estimator and the state spacemodel; applying, by the control circuit, a state estimator in a feedbackloop of the Kalman filter; controlling, by the control circuit, powerapplied to the ultrasonic transducer; and regulating, by the controlcircuit, the estimated temperature of the ultrasonic blade, whereindetermining, by the control circuit, the actual resonant frequency ofthe ultrasonic electromechanical system comprises determining, by thecontrol circuit, a phase angle φ between a voltage V_(g)(t) and acurrent I_(g)(t) signal applied to the ultrasonic transducer, whereinthe state space model is defined by: $\begin{bmatrix}{\overset{.}{F}}_{n} \\\overset{.}{T}\end{bmatrix} = {f\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$ wherein:{dot over (F)}_(n) represents a rate of change of a time (t) dependentnatural frequency F_(n)(t) of the ultrasonic electromechanical system;{dot over (T)} represents a rate of change of the actual temperature ofthe ultrasonic blade with respect to the time (t) dependent naturalfrequency F_(n)(t); T(t) represents a time (t) dependent actualtemperature of the ultrasonic blade; E(t) represents a time (t)dependent energy; t represents the time; and {dot over (y)} representsan observability of variables that are measurable and observableincluding the time dependent natural frequency F_(n)(t) of theultrasonic electromechanical system, the time dependent actualtemperature T(t) of the ultrasonic blade, observable as the temperatureestimator, the time dependent energy E(t) applied to the ultrasonicblade, and time t, and wherein a state variance of the state estimatorof the Kalman filter is defined by:(σ_(k) ⁻)²=σ_(k-1) ²+σ_(P) _(k) ² and a gain K of the Kalman filter isdefined by:$K = {\frac{\left( \sigma_{\overset{\_}{k}} \right)^{2}}{\left( \sigma_{\overset{\_}{k}} \right)^{2} + \sigma_{m}^{2}}.}$wherein: (σ_(k) ⁻) is a variance of state k; (σ_(k-1) ⁻) is a varianceof the previous state k−1; (σ_(Pk) ⁻) is a predicted variance of statek; and (σ_(m) ⁻) is an observed system variance.
 2. The method of claim1, wherein the control circuit and the memory are located at a surgicalhub in communication with the ultrasonic electromechanical system.
 3. Agenerator for controlling an estimated temperature of an ultrasonicblade, the generator comprising: a control circuit coupled to a memory,the control circuit configured to: determine an actual resonantfrequency of an ultrasonic electromechanical system comprising anultrasonic transducer coupled to an ultrasonic blade by an ultrasonicwaveguide, wherein the actual resonant frequency is correlated to anactual temperature of the ultrasonic blade; retrieve from the memory areference resonant frequency of the ultrasonic electromechanical system,wherein the reference resonant frequency is correlated to a referencetemperature of the ultrasonic blade; infer an inferred temperature ofthe ultrasonic blade based on a difference between the actual resonantfrequency and the reference resonant frequency; control the estimatedtemperature of the ultrasonic blade based on the inferred temperature;generate a temperature estimator and a state space model of the inferredtemperature of the ultrasonic blade as a function of the actual resonantfrequency of the ultrasonic electromechanical system based on a set ofnon-linear state space equations; apply a Kalman filter to improve thetemperature estimator and the state space model; apply a state estimatorin a feedback loop of the Kalman filter; control power applied to theultrasonic transducer; and regulate the estimated temperature of theultrasonic blade, wherein to determine the actual resonant frequency ofthe ultrasonic electromechanical system, the control circuit is furtherconfigured to determine a phase angle φ between a voltage V_(s)(t) and acurrent/at) signal applied to the ultrasonic transducer, wherein thestate space model is defined by: $\begin{bmatrix}{\overset{.}{F}}_{n} \\\overset{.}{T}\end{bmatrix} = {f\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$$\overset{.}{y} = {{h\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}.}$wherein: {dot over (F)}_(n) represents a rate of change of a time (t)dependent natural frequency F_(n)(t) of the ultrasonic electromechanicalsystem; {dot over (T)} represents a rate of change of the actualtemperature of the ultrasonic blade with respect to the time (t)dependent natural frequency F_(n)(t); T(t) represents a time (t)dependent actual temperature of the ultrasonic blade; E(t) represents atime (t) dependent energy; t represents the time; and {dot over (y)}represents an observability of variables that are measurable andobservable including the time dependent natural frequency F_(n)(t) ofthe ultrasonic electromechanical system, the time dependent actualtemperature T(t) of the ultrasonic blade, observable as the temperatureestimator, the time dependent energy E(t) applied to the ultrasonicblade, and time t, and wherein a state variance of the state estimatorof the Kalman filter is defined by:(σ_(k) ⁻)²=σ_(k-1) ²+σ_(P) _(k) ² and a gain K of the Kalman filter isdefined by:$K = {\frac{\left( \sigma_{\overset{\_}{k}} \right)^{2}}{\left( \sigma_{\overset{\_}{k}} \right)^{2} + \sigma_{m}^{2}}.}$wherein: (σ_(k) ⁻) is a variance of state k; (σ_(k-1) ⁻) is a varianceof the previous state k−1; (σ_(Pk) ⁻) is a predicted variance of statek; and (σ_(m) ⁻) is an observed system variance.
 4. The generator ofclaim 3, wherein the control circuit and the memory are located at asurgical hub in communication with the generator.
 5. An ultrasonicdevice for controlling an estimated temperature of an ultrasonic blade,the ultrasonic device comprising: a control circuit coupled to a memory,the control circuit configured to: determine an actual resonantfrequency of an ultrasonic electromechanical system comprising anultrasonic transducer coupled to an ultrasonic blade by an ultrasonicwaveguide, wherein the actual resonant frequency is correlated to anactual temperature of the ultrasonic blade; retrieve from the memory areference resonant frequency of the ultrasonic electromechanical system,wherein the reference resonant frequency is correlated to a referencetemperature of the ultrasonic blade; infer an inferred temperature ofthe ultrasonic blade based on a difference between the actual resonantfrequency and the reference resonant frequency; control the estimatedtemperature of the ultrasonic blade based on the inferred temperature;generate a temperature estimator and a state space model of the inferredtemperature of the ultrasonic blade as a function of the actual resonantfrequency of the ultrasonic electromechanical system based on a set ofnon-linear state space equations; apply a Kalman filter to improve thetemperature estimator and the state space model; apply a state estimatorin a feedback loop of the Kalman filter; control power applied to theultrasonic transducer; and regulate the estimated temperature of theultrasonic blade, wherein to determine the actual resonant frequency ofthe ultrasonic electromechanical system, the control circuit is furtherconfigured to determine a phase angle φ between a voltage V_(g)(t) and acurrent I_(g)(t) signal applied to the ultrasonic transducer, whereinthe state space model is defined by: $\begin{bmatrix}{\overset{.}{F}}_{n} \\\overset{.}{T}\end{bmatrix} = {f\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}$$\overset{.}{y} = {{h\left( {t,{T(t)},{F_{n}(t)},{E(t)}} \right)}.}$wherein: {dot over (F)}_(n) represents a rate of change of a time (t)dependent natural frequency F_(n)(t) of the ultrasonic electromechanicalsystem; {dot over (T)} represents a rate of change of the actualtemperature of the ultrasonic blade with respect to the time (t)dependent natural frequency F_(n)(t); T(t) represents a time (t)dependent actual temperature of the ultrasonic blade; E(t) represents atime (t) dependent energy; t represents the time; and {dot over (y)}represents an observability of variables that are measurable andobservable including the time dependent natural frequency F_(n)(t) ofthe ultrasonic electromechanical system, the time dependent actualtemperature T(t) of the ultrasonic blade, observable as the temperatureestimator, the time dependent energy E(t) applied to the ultrasonicblade, and time t, and wherein a state variance of the state estimatorof the Kalman filter is defined by:(σ_(k) ⁻)²=σ_(k-1) ²+σ_(P) _(k) ² and a gain K of the Kalman filter isdefined by:$K = {\frac{\left( \sigma_{\overset{\_}{k}} \right)^{2}}{\left( \sigma_{\overset{\_}{k}} \right)^{2} + \sigma_{m}^{2}}.}$wherein: (σ_(k) ⁻) is a variance of state k; (σ_(k-1) ⁻) is a varianceof the previous state k−1; (σ_(Pk) ⁻) is a predicted variance of statek; and (σ_(m) ⁻) is an observed system variance.
 6. The ultrasonicdevice of claim 5, wherein the control circuit and memory are located ata surgical hub in communication with the ultrasonic device.